Mouse and Trackpad issues

I have some programs where I use my non-Apple mouse with lots of clicking and dragging while holding down either the "fn," "control," or "command" key (or a combination of the above). I noticed a couple of months ago that after dragging while holding a key, my mouse would get "sticky" (it would not want to move smoothly/get stuck for a second until I move the mouse a bunch and then it would move again). This doesn't always happen, but happens, very frequently. At first, sometimes restarting the program would fix it, but now the problem has started bleeding over into other programs after I've been using them.

Recently, my Apple brand trackpad has started having issues with two-finger scrolling - it will scroll a little and then stick and then scroll a little and stick. Not all the time, but it's becoming more and more of a problem.

Yesterday, I noticed that when I tried to hit "Cmd + Tab" to switch programs, the option kept switching back to the option on the left. If I hit "Cmd + Tab" five times, it would make it to about the third option from the left and quickly cycle back to the first one.

Then today, I noticed that in Finder, when I tried to scroll to the right, the panel kept sliding back to the left (almost like a left arrow key is being pressed down continually, though that wouldn't affect finder cause that's not a control feature).

And I just noticed as I'm typing this that the screen that I'm on is ever so slowly, about a millimeter at a time scrolling to the left - about one mm per second in a jerky fashion.

I've tried removing the dongle for the mouse and replacing it and that made it worse.

I've tried replacing the batteries on the mouse and that made it worse.

I've tried using another USB mouse and it didn't improve.

I recently replaced the trackpad batteries.

I've restarted the computer.

I've played with all of the trackpad and mouse (and accessibility) settings in system preferences.

All software updates are up to date.

I have a Mac Mini 2018 running Big Sur 11.6.

Can someone please help me????