Need some help diagnosing the problem:

1992 Jeep Cherokee
Had a bad rear main seal, its been replaced. Now theres a leak from the front, an oil/coolant mixture my boyfriend thinks.
Weird stuff it does:
Temperature is always high, never in the middle unless I'm driving it. what i mean is that whenever I come to a traffic light, or am idling in traffic, the temperature goes up. when it happens frequently sometimes the needle will go into the red and I have to put in neutral and rev it to keep it from going into the red. On top of that, when it idles, the oil pressure goes down to like 20, when it usually is at 40 when I'm driving it.

anyone know the source of this mysterious problem? He's filled it up on oil, and coolant, he's changing the thermostat today. any help would be appreciated. thanks.

is there a milky look when you check the oil.
low oil presure is a bad main bearing and or really low oil level also high heat will make it low psi.

temp always high means bad thermostat.

the front could be any thing from seal to gasket on the water pump and front oil seal high heat would damage both