Hourly rate depends on your winrate per 100 hands. If you were at 5ptbb/100 (aka 10bbs or $2.50) at 25nl and played 500 hands per hour your winrate would be $12/hr.

Nit is a weak tight player.

Ptbb is pokertracker big blind, which is twice that of a normal big blind. So 10ptbb/100 is 20bb/100. Big blind is self explanatory.

Metagame is a term used to describe a different reaction from your opponents that may come up as a result of a particular play. For example if you push the flop on a flush draw and get called, now they see that you are willing to gamble it up with a draw and they might consequently be more likely to play a big pot with a weaker hand against you knowing a draw is well within your range. Their image of you has changed and they will react to you differently than before by giving you less respect.

Also, from the HH's you've posted in this forum you have a tendency to slowplay and underbet the pot with big hands. What ends up happening is that you don't win as big of pots as you could/should have, and also you give people free cards to beat you which can be disastrous when they hit a miracle gutshot after you checked too set and stack off. You need to bet 1/2 pot or more almost always, and usually closer to the full pot against loose passive calling stations. This will build you a big pot quickly and that's what it's all about.

Gl.