The reason for these different value is because these exchange platforms are not in anyway connected to each other, they operate independently of each other.  The only way to know the average price of bitcoin is to visit preev.com or blockchain.info.

Yeah,  I totally agree with you. With the current rate at which bitcoin is going up,  I can say that by the end of 2018, the price of bitcoin will be around $100k. Bitcoin will definitely reach that price by 2018 as there will be more people in the bitcoin world leading to more transactions.

One of the factors that make bitcoin unstable is its volatility. It's the reason for some people's profits and others loss.

Another factor that makes bitcoin unstable it's the fact that bitcoin is not under any government and so cannot be regularised to have particular price in the market. If bitcoin were to be a nation's currency,  it would have been regularised to have a certain pruce with little or no fluctuations.

Yes,  do buy bitcoins. Although the prices of bitcoins are high as if it has reached its peak, it will surely go higher than this. 

It is speculated that before the end of the year,  the price of bitcoin will reach $20000. If you buy bitcoins now, by the end of the year, you would have made profits.

Buying bitcoin now would be the most appropriate if you are buying for a long term investment, say for 6 months, by then you would have doubled, if not tripled,  the capital amount.

I used Poloniex for the first three months of the year but I dumped it for Bittrex when someone introduced me to Bittrex.

As someone who had used the two,  I can boldly say that Bittrex is better than Poloniex. Its general design,  transparency and the support team are better than Poloniex.

However, Bittrex is highly demanding especially when you are about to withdraw, you will be asked to provide your personal information which goes against the anonymity feature of bitcoin.

Having 70 btc is having a lot of money, I'd advise you to figure out your capital bitcoin and sell it. You can then hold your remaining bitcoins i.e your profits.  This can then be used as your capital bitcoin, as bitcoin price is going higher day by day,  you will make profits soon.

Bitcoin can only grow  if the general acceptability of bitcoin grows and this can only be if more people knos about bitcoins and this can only be achieved by educating the general public about the benefits of bitcoins.
We can help propagate bitcoins by advertising it on social medias such as facebook, instagram and twitter. We can help grow the acceptability of bitcoin by telling people about bitcoin

If we could go shopping using bitcoin to pay for the goods,  it means that the general  acceptability of bitcoin is going up which is good for bitcoin.  If more people accept bitcoin as a currency, the price of bitcoin will go higher as there will more transactions than in previous years and there will be higher circulation of bitcoin in the economy.

When the price of bitcoin  was at $8000, I predicted that the price will rise above $12000 before the end of the year so it is of no surprise to me because its a fulfillment of my prediction.

If bitcoin continues to grow this way, the price  will surely go beyond $15000.

There are various ways of getting bitcoins, the most popular being trading.  You can also getting bitcoins from bitcoin faucet but the amount is small.
Another way of getting bitcoins is through bounty campaign signatures where you are required to post a certain amount of constructive  posts in a week.
Lastly, you can mine bitcoins. Mining consumes a lot of power so it is not advisable to mine where there is no cheap electricity.

The only exchange platform I've been using right from time is Poloniex  and I can assure you it is a really good exchange platform. Though I've heard of bitfinex and bittrex, I haven't tried them before so I can't say if they are better than than Poloniex. 
I think it will be better to try each of them out to know which is actually better.

I believe you can actually trade with the small amount of money with you.  But it depends on the amount and the number of months you are ready to put into trading before getting real profits. If the amount is truly small as you said,  it will take a long time for the profit gained over time to accumulate to a large amount of money, as the profits over a small amount of money is negligible, before you can begin to make real profits.

Bitcoin could be bought at any price not just $10000.
When the price of bitcoins clocked $5000, most people  felt that is the peak of bitcoin price in the market,  but there are a few who believe bitcoin can still grow and they are the ones that bought bitcoin at that price.  Looking at the chart today ,  I can boldly say they have gained their profits.
The volatility of bitcoin is what makes this possible. This is actually because no matter the cost price of bitcoin,  the selling price will exceeds it over a short period of time.

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I actually got my first bitcoin through signature campaign on this forum. 
You can get your first 0.000001 through bitcoin faucet but this is so small as compared to what you will get through your first signature campaign here on bitcointalk. 
You can also offer some services for which you get paid in bitcoin.

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I think this depends on the use we are talking about here.
If we talking about making an investment, then definitely bitcoin is better than actual money. Investment in bitcoins is far more profitable compared to actual money.
But when we talk of day-to-day uses of money, i.e  buying of goods and payment of services,  then actual money is way better than bitcoin.

I wouldn't advise you you to quit your job and go into bitcoin full time.  It's like checking out the depth of a river with both legs at a time. As you know jobs are hard to come by these days, it will be foolhardy to just venture into the unknown future.
The volatility of bitcoin is what makes this difficult as there may be a drop in the value of bitcoin leaving you with a double loss.
And if you really want to go into it full time,  bitcoin trading is what should be done part time, lets say 9 months, at least to gather knowledge and have trading experience before going into it full time

Currently, I'd say it's not possible for any altcoin to overthrow bitcoin as the king of cryptocurrencies because of the market value of bitcoin.
Considering the chart,  the value of bitcoin is about 8200 usd while the value of the closest competitor, which is eth, is just 376 usd. Looking at the difference in the value, we realize that it will take years of development on the part of these altcoins to overthrow bitcoin.
But if it does happen, as there nothing that's impossible, I will convert some of my bitcoins to the altcoin and make some investments with it.

Blockchain has been and remain the best bitcoin wallet.
Blockchain makes all transactions anonymous which is good for a bitcoiner.  Blockchain also remains the most secured wallet so I'm rest assured that my bitcoins are safe. Another of the features of blockchain that endeared me to it is its beautiful design.
Its numerous features are just the best for a bitcoiner, so I'd advise you to go for blockchain wallet.