I'm 6'4. Seven or eight years ago I peaked at 219 lbs and was feeling a bit on the chubby side though not that unfit with a moderately active lifestyle. Anyway I took up running every morning and dropped 20 lbs in a month. My set weight was probably 200 and probably still is. I would say 20lbs month one is not a big deal particularity if the weight stabilizes which is what it sounds like in the OP's case.

Light headedness is probably diet not weight or weight loss.

For my personal and professional requirements I like sticking close to 190 now a days which is pretty much middle of the road for BMI but won't be winning me any poke-a-dot jerseys.