2006 Dodge Dakota--High Idle, Revs, Dies while driving

When in park or neutral, engine idles high at about 1500--1800 rpms and revs or surges. Once I put it in drive, rpms drop to about 500-800, which is all fine and dandy. Most of my traveling is at about 35-55 mph over fairly hilly streets, at which time the truck shudders and acts like it's shifting roughly or stuck in gear (i'm not even sure it's shifting. Could be just just trying to stall.) Over the next several days, it shudders every few minutes when I try to accelerate or slow and more roughly until the check engine light comes on and the truck stalls completely, leaving me without power steering or brakes. (This whole process takes about 3 days to reach this point.) I re-start the engine, and for the next 2 days, everything works fine, until the check engine light is turned off (or turns itself off) and the whole sequence repeats.

IAC motor has been replaced, spark plugs replaced, fuel injectors cleaned, vacuum hoses checked and leaks sealed, o2 sensors cleaned, throttle checked, and new software update installed on pcm. Other than that, dealer says computer registers no other issues to address. (Annoyingly, they only want the truck there if the check engine light is on. Yet they say the light registers no code for them to fix. Additionally, they don't seem to care that I say the truck's performance actually IMPROVES as long as that light is on.)

I'm running out of options, funds and patience. Truck has been in shop 5 times in 5 weeks. What's left to check, replace, or clean? I'm now starting to think the fuel pump is going bad. Any other suggestions to try?