OK Let me try and answer as many questions of yours as possible. Bear in mind that although I've been here for a while I'm still technically a "noob" since I haven't gone to that many games.
1 and 2. No. Simply said although they were cheap and perform fairly well there were better guns that you could have gotten (which would have required Age Verification) but without AV there was a better option and that would have been the Aftermath Kraken AK-47 (would have run ~$170-190 though).
3. You're using a Hi-cap ("High Capacity" Magazine) and I don't have experience with those so I can't answer anything about it really but from the videos I see it looks like people are constantly cranking the wheel while firing. For most of us though we prefer using low or mid-caps because of the "realism" aspect.
4. Yes. The battery would be prone to "freezing" and you'll get less performance out of the battery because more charge is required to crank the spring back. Really it's a no-no to play in anything below 0 because of the extra stress being put on the gun and not to mention some gearboxes don't like cold weather and you'll end up getting cracked pistons and destroyed guns which are only salvagable for parts afterwards.
5. For the most part (maybe 80% of the time) guns in the classifieds will tend to be more expensive but they usually include upgraded parts and packages including mags, loaders, batteries, optics, cases, vests, etc.
Example: My M4 was $450 for body, battery, optics it was upgraded and performs nicely. I've seen some guns go for up to $1500+ depending on whats included in the package.
You will however definitely find some guns that go for Sub $300 although they tend to be rarer and don't include too many things in the package. That being said there are retailers who do have NIB Sub $350 guns available and they should perform nicely for the price.
6. AV sometimes is hard to do I understand but it's well worth it. I personally didn't wait too long for mine but I have heard of some people having conflicting schedules and not being able to get it done but the other option is to go to a game, get a loaner and do your AV then because there is usually a Verifier at most games. Sorry but it's policy that the Age Reps do have to see you in person even if you couldn't be mistaken for a 15 year old in any way. They will also be happy to answer any questions you may have about airsoft.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE