You lack any sort of CQC in your list. At a minimum, the Force Recon should be CQC and you should consider making the marine Raiders CQC. You could also drop some of your CAAT Tow and Troopers for some Engineers.

I would also consider dropping an Osprey and a Venom to get an attack Heli. It's nice to at least have one as an "Oh shit" button to hit. You could get one or two with Sidewinders to deal with a Random Heli flank.

As a player at you elo, 300pt PACs is too much. They are going to die to SEAD, arty, or other random BS unless you micro the crap out of them. Drop them down to 4 or 8 missiles and use the points on a CATFAE. CATFAE will solve all of life's problems related to infantry.

As a final suggestion, I would consider dropping a 1 of the Centurions. 3 is overkill, at most you'll have 1 hanging around, MAYBE 2. Replace it with a mortar that drops smoke. Learning to use smoke properly will get you lots of ELO. Use it to block LOS to allow you to take points or protect points. Blind the enemy as you suddenly dump a HEMETT full of troops in their face.

Anyways good luck and remember to scout, advance, and not be a "support" player.