RAYZOON

I apparently must click the song menu, navigate my eyes down to the export option, click there, then drag from the "pill" shape that appears.

Should I be able to use the keyboard shortcuts in Reaper?

An unrelated question: I was setting about learning about the bar editor and there's this stuck kick drum that I can't erase, on the 2nd 16th of the bar, that doesn't show up on the interface. I tried to understand if it was related to something in the brain, but I can't figure it out.

All midi export is working properly for me in Reaper. You have to export from the Jamstix GUI. I have no idea how it would be possible to use Reaper shortcuts for that.

Regarding the stuck Kick, have you tried Bar>Edit>Clear All Notes?

Or maybe it is part of the accents.