There's no way a leaking a/c can contaminate the oil….
When the air is hot and humid it's not unusual to have water condensing on the cold portions of the a/c system…
The only time I had problems with a very hot dipstick was with my '95 E-350 with the 5.8 engine. I was hauling 'just in time' auto parts (put on 280,000 miles in 18 months) and I was using the local fleet store's house brand oil made by Citgo. It seemed to be the culprit as I changed to Mobil 1 and never had any problems with high oil temps after that.
I'm not saying the oil is your problem… just giving you my input.
Living the dream behind the Cheddar Curtain
'88 F-350 Crew Cab, 460 Fuel Squeezer
'97 Ram 1500, '99 Jeep Grand Cherokee. '90 Buick Park Ave.
Plus an old dirt race car.