How to ask my former PhD supervisor to stay away from me and do not contact my prospective new PhD supervisor?
It’s superbly clear: You are being manipulated by a person who possibly has wasted years of your life. At this point, everything they do must be presumed malicious and intentional. Don’t take any other explanations, that’ll be gaslighting. You have to treat your former advisor like a public enemy #1, and his every action must be from now on interpreted as being on a vendetta against you. Look at the last few years. Has that person ever done anything that actually helped you achieve your goals? Don’t think of positive things they said: have they actually been helpful, in the truest sense of the word? Has their helpfulness been of the genuine kind that helps you make progress in the project, or it was only of a kind to put your mind at ease and dismiss the previous horrible things that person has done? My guess: it’s solid NO, they never helped in the last couple of years, and you’re clearly dealing with a manipulator who has no qualms about anything they did so far.
Don’t ever believe any excuses they may offer to recast their abhorrent behavior in a good light. Remember how you felt through this whole ordeal and what a mess it was because of that person. There is no excuse for their behavior. None whatsoever. They are a lost cause in every sense of the word.
Some of the answers to your other related questions seemed to have been slightly equivocal or giving the whole matter some benefit of the doubt. Having had the dubious pleasure of dealing with people like the one you describe early in my life, all your recollections are stereotypical and there's no doubt in my mind that you have been taken advantage of and have been subject of gross mistreatment. The person you speak of is playing a game that takes cards from the same decks that many other such people use. The game they play is so typical and so highly stylized that it may as well be called chess. You see it once and you can't unsee it, pretty much.