2000 Dodge Dakota problem.

Alright here's the deal I own a 2000 dodge dakota 4.7 liter v8 with just under 50,000 miles. When I drive it the car will start out fine for a few miles and all of a sudden when I drive at about 45 mph or so it will pull back sharply. Then the engine rpm will go up to about 2.5 on the gauge and when I come to a stop and try to start up again the engine starts out very slowly and doesn't seem to want to shift. Also sometimes when I am done driving and start it back up again a few minutes later it has a lot of problems starting up, I have to step on the gas multiple times for it to turn over. Also sometimes it idles funny, the rpm gauge will jump from about.5 to about 1.5 without me stepping on the gas. I have 2 fault codes p0320 and p0700. I have recently changed out the battery and don't know if that is the problem. The codes seem to point to a circuitry failure but I am stumped as to what the problem actually is and what I should do.