Vehicle was starting to run hotter than normal?

Right around 98,000 miles we noticed the dreaded "tick" wasn'tt too worried about it as every Mopar I've has done the same thing. Then noticed an oil leak, thought it was rear main seal and took it to shop for estimate, turns out it was oil cooler/filter housing, that plus fixing the "tick" was $3,000.00 more than I had so fixed it myself. I'm 40 years removed from mechanics job so take it for what it's worth.

vehicle was starting to run hotter than normal before oil leak/tick, and felt that heater wasnt really hot enough on cold days.

Now the vehicle will fluctuate between normal temperature and up to 3/4 but only while driving. Will sit at idle forever and not spike. Replaced t-stat with no effect. Replaced coolant at oil change place but they don't burp system, I did and still no change. Heater hoses are hot to touch coolant level is full and overflow is at proper level. No visible signs of leak, no cross contamination of oil/coolant, and fan is apparently operating properly? When the temperature spikes the fan kicks into high speed and stays running until the vehicle is shut off. Also, it seems to get to operating temperature very fast. I can do the repairs, but I am at a loss as to determine the cause and I don't want to throw parts at it till it stops. Also, when replacing oil cooler, it is recommended to replace sensors, which wasn't done, but as I understand it, a bad sensor will throw a code, and I don't have that happening.

Any help is greatly appreciated!