5 channel amp shutting down

I have a sony explode 1505- 5 channel amp (40 X 4 + 150 X 1)  installed in a 93 Ford conversion van. I have (6) brand new 5x7 kenwood speakers(2-35 rms)  (front 2 channels running the front (@ 4ohms) the rear 2 channels running remaining 4 speakers  in parallel). I have 2 - 10" bazooka subs in seperate sealed boxes, running in parallel. It sounds really clean and really loud. I mounted my amp in the middle of the van on a board, and even on 1-1/2" columns on each corner to get ample ventilation. My amp shuts down after about a half hour of 7/8's volume Lots of tight bass too. My question is should I run the subs in series or the rear 4 speakers in series or both or what else could it be. The Amp's specs said it was 2 ohm stable.

  I  just  noticed  that my amp would not turn on right after It   shut  off like normal, so I checked the fuse out and  the 30-amp fuse was melted on one contact??? I put a 25 amp fuse and it worked fine but I need to know what I should do...I know I am overpowering the amp I just don't know how the best way to fix is. Any help is greatly appreciated.

Thanx    jonezy77

Run only 4 speakers at 4 ohm load and runt he sub channel at 2 ohm load. This will probably make the amp last alot longer instead of shutting down after 1/2 hour.

Run the other 2 speakers off the HU and run the subs in parallel if the manufacturer says it'scapable of this. A capacitor will only help if your electrical system is strained but it will not help your amp from shutting down because of the load being too high.