pathfinders like to run below half mark on the temp gage. the fan shouldn't really spin that freely. it should spin but then stop pretty quickly.
don't waste your time with the split boot. they are about as good as the split boot you have on there now. however, they are great as an on trail replacement (temporary.) otherwise they are pretty worthless. if the boots are split i guarantee it that there is crap in that grease that you just can't see. to do it properly you need to disassemble the joint and clean it of ALL the grease then repack and put on a new solid boot. you will have to open up the hub etc.. it's really just time consuming and the bj is kind of a pita to get back in but it's not really that hard.
btw. many split boots are somewhat generic as they normally fit a bunch of different makes and models.