Proper English?

[Maroon]

(It actually is "were", like in "There were "many"/"an unbelievable amount of" presents dropped", since "an amount of" is quite synonymous to "many".)

It's on!
In the case of "an unbelievable amount of", the verb is directed towards an amount, which is singular, so it should be "was", while the case of "many presents" directs the verb to the word "presents", which is plural, so it should be "were".
In the case of "were", the subject is "presents", while in the case of "an unbelievable amount of" the subject is "amount".
/grammarlesson