I'm not qualified nor do I have the time to answer all of these, but to take on a few of them:

1. With the mass adoption of crypto, market caps will increase, volume will increase and Bitcoin (to use that as an example) will be much less volatile. The prices will stabilize at a given point, much like forex does, although even there prices vary a lot. You'll have to rewire your brain to stop comparing BTC's price to fiat; you'll have to think that 1 BTC = 1 BTC. Once you do that, you'll come to realize that its fluctuation really doesn't matter unless it's significant, much like you won't think about the USD's fluctuations on a daily basis.

2. Technically the company owns it, I suppose, but to avoid this issue altogether, just don't store your wallet on your work computer. Store it cold or online, in that case.

3. Part 1: Did you somehow verify the amount of BTC this plant mines? When exactly were they interviewed - could it have been years ago? Was it one of the largest plants in the world? You just have to trust the maths on this one. No one can actually lie about this as you can look it up yourself.
   Part 2: There are probably creative ways to solve this, but they will probably be rewarded by fees.

4. The developer's ambition of making a change. Currently this is actually an issue, as a lot of ICOs raise enough money for the devs to stop caring about their project, and also why a lot of ICOs are scams.

5. Once the market starts reaching the trillions, even the richest people in the world won't really make a difference in the pricing (obviously depends on what coin they invest in), and even if they do bother to invest billions into a smaller coin, they risk the market going against them, especially if their participation is big enough to make a coin more volatile. You don't see billionaires controlling the forex markets to any significant degree, and neither will they do crypto once it reaches its point of equilibrium. If the trading volume for BTC in 5 years is $1 trillion a day, $100 billion will only skew the market so much, and the other $900 billion that day will react to that movement like they would any other.