Hi @Snail, congrats on starting the journey!
From what you’ve written about your test experience, I think @AldridgePrior brought up an important point:
I remember Jonathan saying on the podcast years ago before AI detection of FTP was available, that when FTP test day rolled around his wife made sure there was a bucket handy because his effort was so intense he’d sometimes vomit.
After an FTP test, be it a 1-hour, 20-minute, 2×8-minute, or ramp, you should be absolutely spent, nothing more to give at the moment the test is up. That’s the point, it’s supposed to be a test of your maximum capacity for the set duration. It’s not “oh this is a bit hard now, I don’t like this, I’m going to back off or stop”. 
& I’ve been there. The vast majority of bike interval training with TR will be challenging but not maximal. But testing, by definition, should be a maximal effort.
A couple more thoughts I haven’t seen mentioned here yet:
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Since you’re new to indoor training, check the usual stuff: make sure your cooling, fuelling, & hydration are optimal. (Others will have better ideas; I’m fortunate enough that I can do all my training outside.
) This thread has been an interesting read:
Let's see your paincave! -
Since you do strength training too, make sure you prioritise what your primary focus is (I’m assuming that’s cycling), because fatigue from a strength workout will affect your performance on the bike, & vice versa. And you’ll want at least a few days’ rest after any workouts before you do an FTP test.
So you could take this into account & test again, or as others have suggested just do the workouts, answer the post-workout surveys, & the system will eventually work out your optimal level over the course of a few weeks.