A scenes I found troubling

AS for #2, if I read your question correctly, I believe you are referring to the scene where he & his neighbor deliberately work to make that kid's skis looked worn
(again, THAT kid-neighbor in the scene was also the buyer) because the kid clearly states "My Dad will never go for it" (meaning that kid's father will KNOW something's up if he suddenly appears with NEW skis. I thought kid believed his Dad will likely figure out they are stolen & he'd get in big trouble). So that was my interpretation of why Simon damaged those skis. To my knowledge the only time we saw Simon do this. He wanted to make the sale & even said how he did NOT like damaging such expensive skis. IF I'm wrong & he did again in the movie, my guess would be same reason (to cover his tracks. NOT be caught with brand new skis when skis are being reported stolen left & right.

I know working backward here (because I think--hope-- I had valuable input on #2) but my guess about #1, the cuddling, was that is WAS awkward & painful to witness.
I think unrelated to this scene(to me,anyhow) but there were more than one or two scenes that might indicate his sexual curiosity (where she also catches him trying to watch her change or where we, understandably, see his jealously flash with the guys in her life).
Which would make sense due to his age & add in, how she didn't act as a "mother" but more a VERY bad sister. He clearly (even though stealing to survive) was more responsible, smart, normal (in a sense) & loving. Insofar as the cuddling though, again, I didn't find that as overtly sexual or curious (which maybe kids are curious to see the other sex at his age)... but again, this desperate & WHOLLY sad attempt for relationship, some small sign of affection ...ie: touching, warmth, LOVE & care.
In that scene, he had to pay everything he HAD for just a pinch of NOTHING really.
Broke my heart.
I found it a good choice NOT to show her out partying but just the aftermath. One didn't need to see the obvious. She was not just utterly irresponsible, selfish & lacking basic nurturing, feeling & care but I thought, probably mentally ill. Certainly, at least, unstable! Maybe sociopathic. I can't begin to imagine an honest dialog telling a child how much YOU DID not WANT THEM, and leaving for Xmas of all times! CRAZY mean or plain mental! That is beyond just selfish.

For #1, I think we have to believe it was drugs/alcohol, especially given that she's passed out.

For #2, as noted above, it was to make the skis look used so that parents of kids buying them wouldn't be suspicious.