am I getting dumber?

look at my history, steady decline in cognitive ability. I do these lessons and tactics very day yet just get worse and worse. what should I do besides get checked for Alzheimer's


It happens. Elo rises and drops... Sometimes steady, sometimes dramatically.

I find a slightly different thing. I without question know more and see more than I used to, and have a more effective approach to thinking about positions than I used to (though I don't always have the discipline to use it).
BUT, given what I've learned, I would have expected to gain many hundreds of rating points. In fact, far less. Going up just 50 rating points, I tend to find opponents who ALSO know a lot more than I used to know.
For example, I will play a move which appears to allow a slightly favorable exchange for my opponent (maybe it gives him bishop over knight) but in fact favors me due to opening a file that will favor me -- and he won't take that bishop! Because he knows what I'm up to! Or many similar things. 50 points is a lot.

Well for one thing you're playing blitz which is really just chess lite as far as I'm concerned... I'm sure you wouldn't have missed those moves if you had more time. Also at a rating of 1000 I'm not sure if blitz is the best thing for you to be playing right now. It can be fun for sure but you will need a lot more time to make moves especially at this rating. Try to play some longer games or even daily games if you have the time so you can see these things easier. Anyway, check this out:
Now look at this position:
Do you see now why ...Qh4 loses? If you look at the rest of the game you'll see many examples of this happening especially with the White pieces. So it really just looks like blunder checking problems.