Pertaining to the running hot. My first guess for your engine would be a partially sheared flywheel key. Before you tear it down, look at the hose that comes from the breather. Any signs of oil coming from that hose or if there is any sign of oil seepage from the top- then replace the breather kit and dipstick seals. That could be part of where your oil is going. Another thing to watch is a headgasket that is starting to fail. It won't directly create much oil loss like an OHV engine's, but will contribute to power loss. It wouldn't be a bad idea to pull the head, decarbonize & replace the gasket anyways.

Could be the fan can't get air over the fins. Check the cooling shroud and fins to make sure they are free of leaves, grass, nests, etc.

Having to top up the oil after alternate mowings is a big oil loss. If you were burning that much oil you would have a plume of smoky exhaust. Check the oil level on level ground to be sure it isn't overfilled.

These are good suggestions. If they don't work out or you want to play it safe, you could try taking it to a local dealer or shop. They should know the root cause of the problem.

Here is a link that might be useful: Snapper Lawn Mower Dealer Locator