A/C not working properly

A few years back I purchased My vehicle listed above was purchased from my sister who regularly maintained it in very good condition. She claims the A/C worked fine the whole time living in Philly PA where it gets mighty hot. Since I’ve had it the A/C hasn’t quite worked right. It would get semi cold then clutch on and off more often than expected, and after a few minutes blow warm air. I have researched so many tutorials and troubleshooting while checking and charging the r134a to spec, confirming the compressor and clutch engage, replaced the A/C relay, checked all fuses, replaced the thermistor, the temperature sensor in the cabin air filter, new filters etc. Last year it rarely even engaged but this year I sprayed a little penetrating oil on the outer clutch because it looked a bit rusty and it actually helped a little. I’ve seen decent improvement in the last 2 weeks but still it won’t cycle on after 10-15 minutes warming up until I let another 10 minutes to pass. I’m torn between a bad wire/terminal or compressor clutch. It’s obviously an older (mostly reliable and fun) truck I have spent enough maintaining but can’t justify a $3-700 “repair” for something realistically minor and inexpensive. Is there a general troubleshooting plan for my truck? I’ve got the entire HVAC manual for it which sorta helps but I’m not a pro (albeit very mechanical/tech DIY inclined). I’ll be darned if the shop try’s charging me for the obligatory new compressor and oh yea this dumb cheap harness or connector lol. Ultimately everything appears in order but I’m losing patience on this so any help is much welcome! Thanks in advance. - John