When I was in Israel, I heard someone say וואו מה זה תודה״" is saying מה זה a form of exaggeration?
In slang "מה זה" means "really": "זה מה זה יפה" = It's really beautiful.
No. It's mainly used in fixed phrases like קלות דעת (recklessness), חוות דעת (opinion) etc.
ll קלות comes from קל, the adjective "easy" or "light" (with regard to weight). It means ease or lightness.
ll דעת means "knowledge" or "wisdom", but it's rare on its own in modern Hebrew.
ll חווה usually means "farm", but here I believe it comes from the verb לחוות, which means to express an opinion.
Why not 'what is this knowledge ' (not a great sentence, but you use זה). Why not מה ידע?
This knowledge = הידע הזה, so to say "what is this knowledge" = "מה זה הידע הזה" (or מהו/מה הוא הידע הזה, to avoid using זה twice, which is better stylistically). מה ידע is not really acceptable, it's meaningless.
Knowledge is uncountable. According to Macmillan dictionary, knowledge is sometimes used with a, but only in the pattern a knowledge of something.