I'm not a doctor, so these are just my own personal observations and suggestions.
Finding the reason why your heart got that way is a good step toward moving forward. I believe your cycling is what did this to you. Exercise is good, but this extreme stuff effectively ends up resembling heart abuse. Doesn't sound like you have any blockage issues, so I recommend that you acually exercise or bike mildly, for a year. Your blood pressure has got to be high, so stay on medication to keep it low. Give your heart a chance to relax and "remodel" itself. I think you're the perfect example of someone who can reverse your condition. I believe your condition is from pushing way too hard, so you can't do that anymore. Ride, but just for 30 minutes and not extremely. Whatever the basic minimum exercise per week is. I would try to keep your heart rate below 110. Remember, your heart has overworked to get where it is, you need to exercise mildly, don't lose your temper, and no salty steaks and large meals. Very small and healthy meals are a HUGE factor for low blood pressure. Plenty of sleep and a happy environment should round it up. Get your heart back down to size, then you can ride longer, but never like you use to, or it will get worse.
Ask you cardiologist he/she can tell you. It depends per individual case.
And what stage of HF 1 or 2 or 3 or 4.........I am hybrid 3/4
I am not allowed any exercise. I can walk 100 mtr. And still do my own housekeeping in bits of 5 or 7 minutes. I cook daily. Had to give up gardening, not even patio plants.
Used to do some home exercises up to 9 minutes but due to dizzy spells in my 50s stopped. Homebound only leave my house for medical appointments.