Something’s not right with the fan not blowing at the set speed. I would make sure nothing’s fried at the selector switch and that wiring isn’t hinky where the connector plugs into the resistor. You can follow it around some and see if something’s weird, which is what I’d do if you can’t find it right off the bat. If something shorted out or was bypassed, that could be part of it. I think the second part is related to your alternator/engine speed. The difference in voltage seems a bit much, and if your blower is say wired to the alternator output that would explain some things. That mini serp belt should be tight, no squeaking. I think some twang in the compressor belt with the clutch engaged is fine as long as it’s not slipping. As far as getting colder when the engine speeds up, I think that’s just par for the course in the A/C world. A different orifice tube, assuming yours isn’t plugged up, might perform better just sitting there, but you could potentially sacrifice highway performance. You could check your condensor surface temps all over with a heat gun to make sure nothing’s fishy. Hell, if the thing was just converted over since you’ve had it, and you’re not the one who did it, you can bet the system wasn’t flushed, the o-tube and accumulator weren’t replaced, and the system has plenty of mineral oil in it, which it shouldn’t have. There’s a lot that goes into quality A/C work, and many things can impact system performance.