[full sentence]; thus, [full sentence]. The meaning of thus shows cause/effect, like so, so you would probably use it in a sentence like you would so. The difference is that thus, being a...
Yes, an adverb can modify another adverb. Example sentence: That was really truly the best movie ever.
"Considerably" is an adverb.
Yes it can
Yes, adverbs do modify other adverbs, for example 'He slowly, carefully fit the intricate pieces.'