Another way of looking at it - Windows Solitaire has (or had) a ‘Vegas’ scoring variant, whereby you would be ‘charged’ $52 for dealing the layout, but you win back $5 for each card you put up to the winning line (i.e. moving an Ace from the layout to the top row gains you 5, and so on). It is obvious that if the winning expectation is better than 1 in 5 (20%), the player would make money from the house in the long run. Then you have to adjust that percentage downwards a bit, to account for the fact that in most layouts, you will win back a few without actually completing the game. I don’t know what the average number of cards put up per game is, but it can be anything from 0 to 52 (a completed game).
I do know that my winning percentage on this variant (where three cards were dealt from the deck at a time, you could only use the top card (until it was played, then you could use the next), and you could run through the deck three times before it was frozen) was around 12%. I’m going to guess that of the games I didn’t win, the average number of cards I put up was around 4. So in 1 in 8 games I was +$208 ($260 - $52) and in 7 in 8 games I was -$32, on that basis. Over 8 games therefore I would expect to lose around $16 ($208 - (7 x $32)). This is consistent with my ongoing ‘score’ which would tend to slowly but steadily deteriorate over time.
Now, what I don’t know is whether any casinos in Vegas actually tabled this game with those payouts. I suspect they used to, but a long time ago realised the rate of return was really poor (they have to pay a dealer to deal to one person in order to net $16 an hour before any other costs - if we also assume 8 hands per hour). Plus, I am probably not the most skilled solitaire player out there, I know I often make mistakes - in a casino, only the skilled players are likely to want to play, reducing the casino’s take further. Of course, in the computer age I see no reason why the casino couldn’t put the game on screen, and perhaps they do.
Anyway, the only concrete answer I have for the OP is to their first question, which is about 12% for me - and I think with a little concentration it might be improved to about 15%, but beyond that, with the ruleset mentioned above, would probably be impossible. And I certainly came across many layouts that were unwinnable even with knowledge of where the hidden cards were (some versions allowed you to undo, and/or replay the same deal), because (say) both black sixes were at the bottom of a stack that you could never get to, due to the distribution of the other cards. Or even that none of the top cards you are dealt can be used on the layout, so you never make progress.
I don’t know what the other answers are, but I’d be surprised if someone somewhere hasn’t calculated them.