1) 400 or 500 is common for a 2 hour game or so. Tournaments where you have to play multiple rounds seem to often have 200PV lists.
2) I have the most fun making custom scenarios because I keep finding reasons to think the book scenarios are unbalanced in various ways. In turn my custom scenarios suffer from a lack of playtesting and can themselves be unbalanced, but hey. Still haven't gotten any worse off :)
3) There absolutely are. A few that I think are important to recognize:
Combined fire is way more devastating in Alpha Strike than what you were used to in CBT/Boardgame BattleTech. In chess parlance terms, if you "hang" a unit by leaving it out in the open, you WILL lose it.
As a corollary, losing a mech shouldn't be as big a deal as in CBT/Boardgame BattleTech. A typical game of Alpha Strike has as many lances of units as a CBT game has of units. So losing a mech in AS shouldn't be any more devastating to your side as having a mech lose an arm or leg in CBT. Try not to get overly attached to your units... they're going to die and the only thing you can do about it is try to make the other guy's units die
faster before you run out of your own.
Artillery and Aerospace are fun to integrate into your games because it's so easy to do. Do note the brand new errata.. artillery has had lots of rules changes since the rulebooks came out (most profoundly, there is a rules-set for artillery that is standard rules/tourney legal). In my own (not universally shared) opinion Aerospace has been underwhelming in Alpha Strike, but the most recent errata and the upcoming new PV rollout are both going to help them do better/be more attractive to use.
4) I'm not from that area, but there is a
subforum for finding games here on the site that may be of use to you.
Edit: on point 3... I forgot to mention what may be the biggest tactical shift from CBT: small, fast units are devastatingly good. A big bad assault mech is absolutely not guaranteed to pwn a nimble minx as it normally is in CBT.