You could do peer to peer deals in this forum, or use bitcoin auction websites like bitify that accept bitcoin and where you get items shipped to you after finalizing deals, You could also use gyft and buy a gift card for any online store,
As far as I know, there are plenty of smaller merchants but the biggest ones taking bitcoins (not sure if they still use it) are Overstock, which ships internationally I think.

I don't see what the problem is, The mechanism could be simplified as much as possible, For example, using a hardware wallet, Coins are automatically sent to a new generated address from checkout, This can even be automated, confirmation isn't that critical IMO considering how everyone accept CC payment that MIGHT be stolen and get reversed.

Probably wouldn't go as far as giving it as a gift, because it wouldn't be understood at all, unless the groom is a die-hard bitcoin enthusiast , Seriously speaking I see bitcoin better as a simple gift rather than something official like a wedding gift.

I don't think so, bitcoin is a very solid financial system as a coin and that's my opinion, But banks do cover more than that, giving loans to traders based on their reviews and making profit and giving interest to traders.
That might be because BTC is still too new, but their is nothing like that in BTC and even loaning sites are inefficient now.