Take your points. I think however there is an argument which says - if you have done the practice and you know you can play the piece(s), then at the performance stage you need to trust yourself that you have done the work and can play the piece, so one should therefore be focussing on stuff like expression, touch, tone interpretation, feeling, etc NOT "will I make mistakes".
Absolutely, that shouldn't be an issue. However, you're speaking about it as if thinking about what notes you're playing is synonomous with such thoughts? It really shouldn't be. There's a big difference between focus on what you need to be doing and wondering whether you'll go wrong. The latter is generally caused by inadequate familiarity with what goes on in the former- meaning that the fingers move in a way that is seemingly separate from the brain altogether. Thinking about what you are doing should never cause problems. If it does, it shows that the learning has not yet been thorough enough. You're almost certainly attempting this stage too soon. When performers put these things into the background it's because they know them so well that they can afford to- not because thinking about it might expose holes that would throw them. They have full choice over whether to be conscious or to just play. Also, the just feeling the music is only for performance mode. 90% of practise involves consciously noticing what is going on, and reinforcing the reflexes that might come into play within performance. The classic mistake is to get something right a few times and then try to never think about it again. To keep things working, you have to keep going back to thinking about them.
My mind tends to be NOT focussed at all, simply hoping I can get thru the piece(s) I am about to start. I try to relax physically (bodily) and focus on that as much as possible. But I don't ever seem to reach a single point where I can say "now I am ready to start", I just tend to just play.
Some people might go down the psychology road here, but if you're worried about getting through at all, I have to say that it strikes me that your practise is not preparing you for going into full performance mode in a useful way. There are doubtless issues that are either technical or regarding how you think about the music that need to be developed further first- so you can go in with confidence in what you are doing. Focussing on the musical issues may well help, but you have to be sure this involves noticing harmonies and intervals etc- not turning off to such issues and hoping your fingers will work on their own.Visualising the notes you are to play is a part of musical thinking as much as thoughts regarding phrasing and shaping. If this is not currently happening, it really needs to be.
Why not film a short excerpt of something and upload it? To be honest, there's a limit to what can be said without seeing how you move.