Lucky you because I stopped playing for a week and went from playing 5* to not even being able to to pass a 3* but I think it might be because I got covid
(I'm actually really infuriated by this)
That aside, take a break. It's not good to force so much strain on your hands and fingers constantly. You'll injure yourself very easily if you do that. Also while going up rank is cool and all, it really shouldn't matter to you unless you're a top player. I don't think you'll lose all of your abilities from a hiatus, although of course it depends on how long said hiatus will be.
Hey and in case it makes you feel any better, my skill cap has been the same for about 5 months. Also sorry for crappy reply. I can't really think of a response
Edit: Actually just stop focusing on pp farming. Unless you consider it fun, stop doing it and take a break. You don't have to take a break from the game entirely, as you can just shift your attention to easier maps or maps that require different skillsets. You only have 1 SS, so maybe try acc training for a bit. Remember, rank and pp do not determine skill. Maybe try ironing out your skillsets that you don't really excel in (or just every skillset in general) to balance and strengthen yourself out as a player and then go back to pp farming.