Can the verb Passar, when translated to 'to spend' also be used in terms of spending money, or is it only used for spending time?
Passar only works as spend to refer to time. Spend money = gastar dinheiro. Waste = gastar, desperdiçar.
I was told that "gastar" can be used with "tempo" as well. My question is: can it be used without the negative connotation the verb "waste" has?
Yes, you can! Gastar can have both positive and negative connotations.
But "desperdiçar" has only a negative connotation.
Why in this sentence “too much” is not accepted as translation for “muito”, when in other similar instances what gets rejected is the simple “much”. I feel like I am missing something here and I would appreciate some background to help us decide whether “muito” means “much” or “too much” based on context.
Because that has a different meaning. See:
Your sentence means that you have travelled through Asia many times.
Duo's sentence means that you stayed in Asia for a long time: it could have been many travels (as you said), but it could have been just one single loooong trip.
Yes, but the same still applies: I passed/spent a lot of time in Asia and I passed through Asia many times have different meanings (as I explained before).
The problem is not the verb, but using "through" instead of "in" and using "many times" instead of "lot of time"