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Question: Is there a way to tell if my compressor is bad vs. a clutch problem vs. "just" low pressure?

1997 F-150 4.2L Manual: My A/C compressor began cycling on and off constantly yesterday, but not at consistent intervals -- may be 2 seconds on, 5 seconds off, 10 seconds on, 2 seconds off -- you get the idea. It makes a LOUD noise when it cycles back on and also feels like it "jerks" the truck when driving (for lack of a better description) when cycling back on. My #1 suspicion is that the compressor is seizing up, and the noise and "jerking" when driving is because the belt is pulling so hard to try to turn the compressor. (Please excuse my lack of knowledge of all the proper terms for what I'm trying to describe -- hopefully it's coming across one way or the other!) However, a part of me is hoping it still may "just" be something in the clutch itself or the pulley, or something off in the pressure due to low coolant. The pulley is free-spinning fine when nothing is turned on to cause the compressor to try to run. All I had time to do last evening was use my father-in-law's low-side gauge (I know, I know); and it did read low, and I added some freon. No change, but I know I need both gauges and a real check. This evening I will be able to check low and high sides with "real" gauges and remove belt to check clutch and pulley assembly more thoroughly, so I just wanted to ask if anyone has thoughts on this? Advice on what to check for? Should I even do those things at all or go straight for the compressor? I've seen some things about compressor bearings, but confess to a complete lack of knowledge there and haven't had time for research yet. Any help on that? And, I 100% appreciate all the help I can get from those more knowledgeable than I, but I will go ahead and save everyone typing time by letting you know that if I need to go to the compressor I know I need someone who has the equipment and knowledge to vacuum the system, etc. :-D Thanks so much for any help I can get!!!