1. What is the best way to do this? Exchange without KYC? Atomic Swap? (NO centralized exchanges)
As far as I know, you cannot directly exchange your BTC to DAI, and upon checking, Uniswap
[1] has the most volume right now. However, you Uniswap only has DAI/ETH trading pair which means you need to trade your bitcoin to ethereum first, and then trade your ETH to DAI.
You can use bisq
[2] to exchange your BTC to ETH if you really want to avoid centralized exchange and do not want to undergo the KYC process.
2. Which wallet should I use to store DAI ? (I'm a little scared to keep such a sum of money in a meta mask in my browser)
Are there any analogues of electrum for ether tokens?
DAI is an ERC-20 token which can be stored to ERC-20 compliant wallets such as Metamask or MyEtherWallet and the only thing you can do to increase the layer of your security is to integrate your Metamask wallet with a Ledger or Trezor hardware wallet which can cost you for about $100 - $200.
3. I chose DAI because of its decentralization and the inability to get a coin lock. Do you think this is correct? (I will keep the DAI for about 1-2 years)
@mk4 has a better explanation in terms of asset-freezing for DAI.
Single Collateral DAI(SAI) and Multi-Collateral DAI(DAI)
Besides USDT on the Liquid network(which isn't really THAT accessible right now, hopefully in the future), the DAI/SAI stablecoin, which is both from the MakerDAO project, are the only stablecoins on the list that's unfreezable as you may see.....
Also, not because DAI/SAI are unfreezable right now, it doesn't automatically mean that it will be like this forever. Remember, there's still a single core team working on this project, and they can easily change the code today if they wanted or needed to. Not because they're bad people per se, but they might need to comply to government's requirements sometime in the future.
[1]
https://uniswap.org/[2]
https://bisq.network/