1996 Chevy S-10 S-10 oil pressure problem

I'm a young learning mechanic so I'm not sure what the problem is here. During idle I have a rough vibration which at first I assumed was from the driveshaft (I've heard this was a common problem in S10's). But, the vibration also occurs in park and neutral. It gets steadily worse as the engine temperature goes up. And recently its been going higher than I've ever seen it, but I attribute that to the extreme summer heat. But as the temperature goes up, the oil pressure drops as low 20 - 25 psi at idle and about 50 psi while accelerating (while its normally always been 40 at idle and 60 while accelerating). I believe the vibrations are associated with the low oil pressure now. As well, if I brake too quickly say from 40mph to 10 to make a turn, the engine seizes from the dropping oil pressure. Please give me some guidance as to what this problem could be and where to check first. Much appreciated.