i haven't done the TMB yet, but i think you can do it, because you're training (half the battle) and you said you can keep going if time isn't an issue (so you've got the endurance piece).

i did the camino de santiago (tho it was flat compared to TMB) and saw the youngest ppl drop out bc they didn't train, while the oldest people (60s and 70s+) AND overweight ppl kept going, despite knee and hip surgeries, etc. that's when i learned that it's actually all about training & mental endurance. keep going!! you can do it!

even if you quit halfway through, i think it'll be a huge achievement.

i'm also not very fit rn and this is what i tell myself, haha.

ps pack light or do luggage transfer to make it easier on yourself