I agree with Jace that the sternguard are probably better having combi-weapons of their own. I would also take the power axe off of the sergeant since pedro is in the unit with his fist anyways. Frees up some points.
Meltaguns. Meltaguns everywhere. Keep in mind that for meltaguns to do their best job they have to be within 6" of the target vehicle. Most smart enemies will easily stay out of your tactical squad's melta range (who are probably sitting still on an objective anyways) so I'm not entirely sure it will be the most useful there except on the combat squad. Maybe switch the missile launchers for Multi-Meltas? Twice the range, twice the threat. Works much better on objective holding tacticals.
I like the plasma you have in the list, I think it's a highly underrated weapon choice. I'd use it myself but I don't have the plasma guns model with. Maybe switch the aforementioned meltaguns for plasma? It'll more than likely make its points back.
I also agree with Jace on the power fists being a bit much. I know it was (is?) all the rage to throw a power fist in every model you could, but I never saw the point in it since marines are far *beyond* awful in close combat anyways. Even the simplest of CC assaults can sweep a marine squad off of the map let alone an objective. Yeah power fist kind of adds to that, but for probably a single round of combat, then will die. Just never saw the reasoning for so many points just to die as soon as it gets into close combat, which is where it *shouldn't* be anyways. Just my personal opinion though.
If you can find the points I would highly recommend switching the predator's turret lascannon for the sponson lascannons. Two LC shots at BS 4 are better than a single twin linked one, especially since over the course of the game it's firing many more (accurate) shots. Would really help your ranged anti-tank a long ways.
Lastly, while I don't mind the Plasma Cannon Dread, I would just like you to consider switching to a lascannon. Would give that extra anti-tank/monstrous creature oomph from a large range. Whether you do or don't It would be a good idea to give it a missile launcher on its other arm. That close combat weapon isn't going to be doing much from 36-48" away. Missile launcher will (just not much).
Overall though I like the list, lots of special and heavy weapons of every kind, very diverse. Hope you find this helpful.