For convergence, its all about how you want to deal with your opponent.
For example, if you are able to get in close on a regular basis, set your convergence for 300.
My settings are usually 500-600 as I am not too good at manuevering yet.
As for evading a 6 oclock baddie, it depends on your plane. If they're in a faster plane, odds are you can evade him by getting slower.
Let him get to about 600 (800 if he's high speed) and yank back on the stick, cutting throttle to half or 1/4, drop flaps and then slowly nose down. Usually you'll make a "hump" which he'll attmempt to follow but when soars down when you're going down, he'll over shoot and thats when you raise flaps, punch the throttle and nose down.
If you're in a manueverable fighter, trying decreasing thottle to increase turn rate and add flaps. If you're in a high roller (FW, Jug, etc), try snap rolls to confuse him and lose speed.
Now what I recommend is find an AH friend. Wing up with people. Having one guy that can follow your six and cover it build's confidence.
And remember, if you're shot down don't get angry. Take a deep breath and think about what happened in the last 10 seconds before getting shot down.