The only suggestion that I have is to keep working at it. I know that's not much help, but when weakness set into my left arm and leg, I had trouble, playing guitar. I needed my left hand to hold down the strings. I use to be very good, but then I had to start from scratch, like I had never built up the strength in my fingers. After about a year, I feel, I'm slowly building it back.
As far as the language issues, I do this too, but it seems to come and go (Thank God). I've had the opposite problem with my strike keys. Sometimes I will get a tremor in my hand that causes me to hit the button more than once.
My memory use to be very good, and still can be, but I will often go through spells of forgetfulness, so I write everything down. I use the "google task bar" spell check all the time to check for errors, and for the bigger things I write, I use Microsoft Word that checks both spelling and grammar errors, then I will transfer it with copy and paste.
It's really hard when you use to be able to do something, and then BOOM...it's gone. Hopefully we can all get a little bit of ourselves back, even if we have to rely a little bit on technology to do it for us for a while.
I can relate to all you've said, what to do about it is something i've not found a solution for, though i'm always looking. I did try learning to write all over again, calligraphy i cant remember well enough to pull it off for long but i did find when i was an assistant in the prep room, i had to think before writing each letter and that seems to help a lot, though very time consuming.lol.
It's been years since i let anyone see my writing, my best is still quite scrappy and embarrassing, i've got away with it for a long long time, it isn't something that comes naturally anymore, its an effort for it to even resemble how i use to write, and made worse by the disappearing spelling. If i have to write i always use a keyboard, nothing gets sent with out spell check and proof reading, though i'm a little slack doing it on the forum due to the length of time it takes to compose something, and i know i wont get picked on because of it lol. I also carried around a little spelling book that i used all the time until i couldn't see the tiny print anymore, for some reason everyone thought they needed one too, so didn't look down on me using it.
Other than that i've been using smoke and mirrors, i also look forward to anyone elses input.
Cheers.........JJ