It’s a bit hard to tell with that short of a training history to go off of but…
You had been doing a lot more volume. You had a string of several weeks that were 13-22 hours and then it dropped significantly (probably lockdowns and colder weather) to about 4-6. Volume (even low intensity) plays a large part in VO2 so I’m not surprised that your power would fall. If you can, I would add some longer rides to the low volume plan while you are stuck inside. Long trainer rides can suck but I’ve found that with some form of entertainment (movie, TV, bike racing, youtube, etc) I can get through 3 hours without too much issue.
However, the caveat is only do more if you can handle the additional stress. You say you probably don’t sleep enough and have a stressful job. Both of those things can severely limit the amount of training stress you can handle as well as how well you adapt from it. Then add in the not so obvious stress of being stuck in your house during a global pandemic. It’s possible that those long outdoor rides you had been doing not only were good for your fitness but also for lowering your stress. So maybe you need to be more diligent about finding other ways to lower that.
And finally, maybe the ramp test just isn’t great at modeling your FTP. But without HR data its a little hard to see how the workouts correlate to one another. Do the threshold workouts at the ever lowering FTP feel easier and easier or do they seem to stay consistently difficult?