What about "This pair of shoes", like is grammatically correct?

Correct grammar on your sentence would be: "This pair of shoes is too small!"

That's because that sentence is incorrect in English, too

This pair in English

You can't say "these pair of shoes" in English. However you can say "this pair of shoes" or "these pairs of shoes"

Well that isn't correct English, pair is singular not plural. "This pair of shoes is too small" is what you want.

That's accepted now

太……了 is used to put emphasis on something. E.g. 太好了！Fantastic!! 我太爱你了！I love you so much!