Welcome to TrainerRoad and to the forum! Sorry to hear that you were sick, huge bummer but so many athletes have been experiencing that lately, and luckily, Adaptive Training is designed to accommodate your current fitness as you ease back into training.
In asking if you should either decrease the intensity of your workouts, or manually lower your FTP, the answer is: neither! 
You absolutely did the right thing by marking your recent Sweet Spot workout as ‘Too Intense’ when it felt that way, because it gave Adaptive Training the opportunity to do all that adjustment for you by updating your future workouts and taking off a bit of that intensity to put you at a more achievable level.
@PhydomiR is right in that “Manually editing also works but that would require you to know your body and capabilities very well”, and this is where Adaptive Training really shines and takes that guess work out for you. You’ll see this too when you start feeling like yourself again and AT recalibrates quickly to make sure you’re challenged by productive workouts that keep moving you forward.
I also want to go over some options for you in the future when you’re not feeling 100%, where you should feel free to just select an Alternate to your scheduled workout if you still want to try to target the same goal of the workout but at a different workout duration, or to just grab an endurance workout via TrainNow if you really just need to chill that day.
Adaptive Training will account for all of these changes too when looking at your future workouts, so definitely listen to your body as you’re getting back into things and don’t be afraid to make changes like this.
Finally, ‘How far back does the FTP detection look at rides?’: I hear your concern that it may not be looking far back enough or fully understand your 2 months off, and while AI FTP Detection looks at your most recent training, its definitely addressing workouts beyond just a couple months ago, don’t worry.
It’s also important to acknowledge that easing back into training after regular ‘time off’ will look different than if you are sick, which is why the post workout surveys are so important when you’re struggling. It adds that context to Adaptive Training so that it’s understood where you’re at in your fitness and how to ramp you back up appropriately; and it calibrates in that way really quickly as we’re seeing in your case!
Your bases are covered when you respond to those surveys and let AT apply adaptations that reflect your fitness. Nice work answering those promptly!
If you have any lingering questions about moving workouts, your survey responses, Adaptive Training, etc., please feel free to message either myself or @sarahlaverty, we are TrainerRoad’s Community Managers and super happy to help take a look at your calendar and workouts anytime! 