Japanese works differently than English. の is used to join two nouns, with the first modifying the second.
book の reader → the book's reader, the reader of the book
dog の keeper → the dog's keeper, the keeper of the dog
Sometimes the relationship works out a little differently than the above, in which case you must rely on ...
These two are distinguishable in speech, because when you mean #1, you are going to say the whole phrase in a single intonation block, but #2 will be two: 抑えられない／幸せにしたい気持ち, reflecting the structure that two chunks being parallel modifiers of the last noun.
If written, it is ambiguous in theory. I said "in theory"...
Yes, this そんなん is a colloquial version of そんなの, which in this context means "such a guy".
This use of の/ん as a pronoun for a person sounds rough and/or arrogant. The first example is natural since he is already referred to as やつ. On the other hand, the second example sounds condescending and unnatural. You usually have to say 優しい人(が好き)です or 優しい男性(...
私は出来るだけ静かにしていた。 I kept as quiet as possible.
The する, used with the continuative form (連用形) of an i-adjective or na-adjective, or an adverbial phrase such as こう、そう etc., is an intransitive verb meaning そのような行動や態度をとる ("to behave/act in a particular way").
Adjectives are words that modify nouns, whereas adverbs are words that modify adjectives and verbs.
By adding に to a na-adjective, you turn it into an adverb. In this way, 静かにする can be seen as the adverb "quietly" directly modifying the verb する "to do":
静かにする。Literally "to do quietly", i.e. "to be quiet".
I think ...