Have a closer look at your power for the race, you could’ve started off way too hard and then struggled to hold your power, RPE doesn’t regulate your effort well in a TT, they tend to feel easy to start with and then get more and more desperate as you go, average and NP won’t reflect this, you have to dig a bit deeper.
I have found that what my theoretical FTP is and what I produce in TTs can be very different, both plus and minus. As Lance once said “some days your the hammer, some days your the nail.” Also worth bearing in mind outdoors vs indoors is very different, holding position outdoors on a TT bike is hugely physically more difficult than sitting upright on an indoor trainer, it is normal for most people who are new to TT to have a large discrepancy between their trainer tested FTP and their outdoor TT bike FTP.
That said your gap is quite large and a solid 40min effort should give a good indication of FTP as Coggan states it is an effort that can be sustained in a steady state without fatiguing for between 40 - 70 mins. If you are able to get through the workouts as prescribed then stick with your current FTP, if your struggling it might be worth retesting, maybe outdoors on your TT bike to get a more accurate figure. I have found that the ramp test doesn’t work that well for me so use the 20min test, plus it is a good workout which practices pacing, so it might be worth considering that.
Final bit of advice, the bike I use on the trainer is a normal road bike but with clip on aero bars, once I’m in build and speciality I do as much of the intervals as I can in aero position, it’s not the exact same as my TT bike but it has helped bring my aero tuck power up to my normal position power.