Thyroid best medicine. To become fit.

Hi I have hypothyroid and level went to 8 , it was 11 and I was given Eltroxin 25 mcg , came down to 7.5 , now after lockdown lack of work out and movement checked thyroid it is 8 now , doctor suggested Thyronom 75 mcg. For a month will it bring down my thyroid level to normal. Also i have a few tablets of Eltroxin left of 25 mcg . Can I finish them off by using 3 tabs each day to match upto the 75 mcg Mark. Also I am non Diabetic and my fasting sugar is always around 80-85 , now almost a year gap of tests and no exercise like I am an active gym goer and Swimmer , walk 4-6 kms too, but for Covid completely at home so , have put on weight , not much though, but just had a complete body check up and found that fasting sugar came as 105 and HBA1c came as 6.5 , so need help to get back to normal any suggestion Doctors please.Please note I do not take Sugar or any sweets , and even rice very less only once or twice a week , completely on Chapati's , fond of potato. Need help to become fit.