Sonterra Meeting $2/$5- To Fold or Not?

I played poker after our visit to the stores and did well. Bought in for $200 and cashed out for $800. This happened at Sonterra.

Me: 9 10 off in position running well called raise to $15. Flop is 78x. I call a $25 bet. Turn- K, he leads out for $75. I put him on nothing more than a pair or over cards. I calculate my odds to the open ended draw and estimate I am 5:1 dog. Money is 160:75 or approx. 2:1. So I fold. Mark was sweating me and said I was wrong for folding because I would have stacked the aggressor ($400 or so- possible but likely he would put in 60%-75% of his stack or $300). BTW the dealer turned over the river and it was a 6. Aggressor said, upon seeing the 6 that we would have chopped it. I asked him how he knew that. He said he would have made the straight to the 9. I would have made it to the 10. I was second guessing my decision but it was based on preservation rather than accumulation.
Thoughts?

Another hand I was dealt 55 in late position and I called a raise to $15-$20. We took the flop 3 handed and it was 56J rainbow. Original raiser (Charlie) bets $30 into the $70ish pot and gets called so, I plan to isolate against possible straight draw and make it $80 so it's not a prohibitive bet. Original bettor (Charlie) throws up all over the pot and goes all in confidently. Sandwich guy shows others not in hand what he has and lays down (turns out to be AA). I go into the tank and immediately put Charlie on 66. I show my hand to people on my side of table- Randy admonishes me for not calling instantly as I am making Charlie feel like he is good. I told him I'm not convinced I should call and turn my hand over for a reaction. Nothing. After more deliberation, I fold and Charlie shows his 66 for a higher set. No reason to put your money in bad if you're sure or somewhat certain.

Antother hand I am dealt A7o and make a pre-flop raise to $15 and get 4 callers. Flop: TTT! Checked around. Turn card is 7. Checked to me and I bet $40. Fold around to Randy who check raises to $100. I call. River is an 8 and Randy leads out for $150 and I call with the 7 and he mucks. I believe this is an easy call on my part as the unlikelihood of him having a 10 there combined with me matching one of only two cards on the board and his ability to play with chips is enough to give me the green light there. I stacked about $460 on that hand alone.

So Thence It Began

My journey into self analysis, observation, assessment and ridicule begins.