He eats as much as I.
instead of this sentence, can i use He easts as a lot as I?
As… as is an idiomatic expression You need an adjective to be placed in between the construction 'as ... as'; as:
as black as pitch, as busy as a bee, as clear as crystal.
A lot is two words, so it is a phrase, which can be used as noun, adverb and some times as adjective.
Second, It seems that as you said, "a lot" can't stand for "much" because it is a phrase of two words, can it ?
I think the reason is that "a lot" is neither adjective nor adverb, it is usually used with "of".
Please explain more and if possible show some examples.
Thank you !