Ford Truck Enthusiasts Forums - Power loss and oil sprayed out dipstick

Hi everyone!
I am new here so tell me if I didn’t post at the right place or if you need other info.

I went for a long trip with my Ford 20 ft motorhome 1976 460cid and got issues. I always look for hours on the Internet and under my hood or go to see my mechanic, but this time I am far from home and I am kind of stuck.

We have a loss of power that first happened while driving on a steep hill while the engine seemed to overheat. The gauge would not go further than just before mid-way/half which seems to be a normal range. But after I stopped, I could see some coolant sprayed out under the hood. It happened twice.

Then it started to lose power after a 20mn drive and last time almost as soon as I went on the highway, but no overheating. - When the second overheating happened we also saw some engine oil sprayed out from the deep stick (quite a bit, enough to have to add some) and in the air filter (a few ml). After that, it happened every time the engine would need to work harder.

When we bought it, one month ago, there was some milky oil on the dipstick after one or two drives. I showed it to my mechanic (I was thinking about the head gasket) but he explained that it was condensation because the oil in the pan was clean and it was only on the dipstick. No loss of coolant, clean coolant and the engine was running really good.

Since all those issues happened, we changed the PCV valve and I think it did not change anything because I am pretty sure that a little bit of oil still gets out (I didn’t really get my engine working hard enough again for it to really spray out again as I have a loss of power too quickly. But when the engine is hot, I see some thin smoke coming out from the dipstick when I take it off).

Last night we checked the cylinder pressure (I was thinking about rings) and we got:

Rear 130 / 115 / 140 / 145 Front
140 / 130 / 120 / 130

All cylinders went directly to around 90 at the first circle, then 100/110 at the second and almost to their max compression at the third cycle. I understood that those results are not indicating something bad. The 115 is not supposed to be badly low, right?

I am sure that I did not put more oil than the max on the dipstick but during this long trip I put the max oil level at some point (when I usually try to fill it middle to 3/4 level). So, this morning I dropped the oil (changed the filter also) and put a 5QT in it to check if the dipstick wasn’t wrong. I got the ¾ level on the dipstick. I looked on the internet to know the capacity but I got many different answers from 5 to 7 Qt. How to know the exact capacity? If it is 5Qt could I have overfilled it and damage the engine?

I am a little bit lost and I don’t know what to check or to do next! Can you give me some advice please?
Thanks for your time guys!
Gui and Anna