It is possible to maintain a high level, and I have a possible solution. Firstly, especially with time restrictions, you should be doing much more work in less time, so use your more difficult skills as exercises. If you can consistently do sets of 5 freestanding handstand push ups, that would be great to base a routine around. If you have to though, just use the wall. Perhaps even better, though, is you’re doing waaaaay too many reps for your core. You should do harder stuff like V sits, full hanging leg raises, and dragon flags because you will be training more for strength. The great thing about it, though, is that you will be saving a ton of time on your core work which can go to other aspects of your training. If you can’t already, I’d suggest training for the stand to stand bridge and the one arm pull up. Also, pistol squats.
A good, quick workout could be like this:
Handstand push up
Pistols on left leg
Pull up or hanging leg raise
Pistols on right leg
Then do bridging as a warm up or cool down for a few minutes. This will allow you to hit pretty much everything pretty well, and you get a bit of rest by rotating between muscle groups, so it will be easier to minimize rest times.