As @
wphamilton mentioned it’s very challenging to return to form following an injury. Yours is even more challenging given you had some physical damage plus serious issues with your cardio system from the TB. It does take time. It sounds like you need both endurance and some interval training to get your cardio back in shape. I’ve been through it a few times from both injuries and illnesses and it takes effort. It’s actually pretty darn tough work but you’ll be tickled with the long term results.
For cardio you might try going as hard as you can for short periods, 10 seconds?.. 30 seconds???? 60 seconds??? Whatever you can do to geet your HR up quickly. Do 3-5 sets and add both time and frequency as you get stronger. For endurance you just have to log time in the saddle. Can you plan to ride to a destination to get the miles you need?? That usually works for me. Once I get there I know I have to ride back.
Sorrow about your issues but recovery can be rewarding. Good luck!!!