Yeah this sucked.
I couldn't get any help from Boomerang, and I had no HE artillery option either. I thought about going back to the main camp to get a tank or something but I was scared that Boomerang might die or something and the mission might fail. In the end I just killed all the guys really slowly and painstakingly with lots of dying and reloading.
When they were all dead, I found rocket launchers on the dead bodies and I peaked out from behind the stationary APC type thing, and I shot the tank and the enemy APC that was patrolling the area. With those dead it was mission over. It's a shame because it could have been fun if it was... a bit different.