Getting involved with a friend's mom

Alright guys I need some advice. In a real bind here.

Three months ago I slept with my friend's mom, let's say her name is Linda. This guy isn't my best friend but he's right up there. He's in my band. Anyways I know he has no clue. But I noticed he started acting like a jerk to me for totally different reasons, because I got angry that he borrowed this Slayer album off me and gave it back to me scratched after he burned it and put it on his iPod. So that started making me care less and less that there was something between me and his mother.

Now, his mom is sort of like, the last suspecting married woman you would expect to cheat on her husband. So one day I was at the general store on the side of town my friend lives in and I saw her walking past the parking lot. We said hello and I asked her if she needed a ride because she doesn't have a car and used to have to walk pretty far. She's dark haired and very nice, and she obviously has known that I smile at her way too much and am too nervous around her. Because she kissed me on the cheek when I dropped her off. Mind you this lady is like over twenty years older than me and in her mid 50s. I basically just said "thanks" and sat next to her in the car feeling extremely awkward and light headed, then we started kissing. This is in the drive way of their house, but which is totally hidden from the rest of the street, and there were no other cars there. So we kept making out and I felt her breasts through her shirt, she felt around my crotch but didn't really grab my penis. But she could definitely tell I was really hard. I asked her when people would be home and if her son would be by to pick up the rest of his stuff (he was moving out). The coast was clear, and I asked if I could go inside to use the bathroom (haha). She said, "sure you can come in to use the 'bathroom,'" and said it like it was italicized. We basically walked in and immediately fell on top of eachother kissing, feeling, and had sex and I came very soon, which really disappointed me (and doesn't usually happen). She seemed disappointed too, and to regret the whole thing, which was quite shameful to me.

My first question is to guys here: what should I do to get better in bed with this older woman? My sex life with my girlfriend is sort of mild, and it lasts for a long time and I usually have to receive oral sex and ejaculate in her mouth just to cum. But with this woman who I will definitely see again in the future just makes me into a 13 year old, lol.

My second question: should I try to fight my "friend"? Not only did he scratch up my Slayer album (Reign in Blood), but now he denies doing it, and made fun of my brother who is dyslexic (I Know retarded, right?). He is just a really cruel jerk and all of my other friends think so, he always tries to act so macho. Seriously, this guy gloats about having killed mice and crap, like torturing small animals makes him tough somehow (even though it really just makes him pathetic). It's hard to see how she gave birth to this piece of crap, to be honest. I don't feel guilty at all about having been with his mom, but I don't want him to know. And then the last time I saw him, he stiff shouldered me. Should I ask him to fight me and settle this like men? And if I do, will his mother still sleep with me?