Details:
Husqvarna LTH18542 w/Briggs &Stratton 18.5hp, OHC, ELS500

Also seems to be a conciderable amout of oil (very small droplets) being blown out of somewhere near or maybe over the carb.

When pushing, it isn't abnormal to have some drag really. Much more so if the hydro release lever isn't engaged. If those oil droplets are coming out of the breather hose to the airbox- it would seem to me that the headgasket may be the culprit. That is if the sump has straight oil in it. The stall may be several things. If it seems like a switch is being shut off when engaging the deck or let the clutch out- first thought would be the seat switch or connector.

Did you address the crankcase full of gas issue?
Is the air cleaner element clean & DRY?

Tomplum-3 x harder to push back than forward and each direction is harder than I remember. Sump does have straight oil in it. I will check the seat switch again, I notice the stall happens before physical strain is placed on belt. I'll check circuit and reply. bill_kapaun- new nv and shutoff and flushed all out. Air cleaner clean and dry.

Addressing the issue of gas in crankcase oil means: Did you change the oil after fixing the gas leak?
Gasoline in the oil will begin to boil off when the engine warms up.
The evaporation of the gasoline inside the engine will develop pressure inside the crankcase. This pressure then vents out through the crankcase breather facility and hose that leads to the air cleaner housing. If the breather hose is properly connected to the air cleaner housing...... the vented gasoline vapor stream gets fed right back into the engine, along with any fine droplets of oil that hitched a ride out of the frothy lube oil in the crankcase. this will make a lot of smoke out the exhaust.
On the other hand......if the crankcase breather tube IS NOT properly connected to the air cleaner housing, you may see what looks like an oil leak with a lot of small droplets of oil coming from somewhere near the carburetor or air cleaner area.

Thx for your input mownie! The first time I found gas in the oil, I made repairs and changed out the oil and ran engine for 15 mins, smoked for the first 10. Next day found about 1 qt. of gas in crank and repeated the previous days routine, but this time I shut off that damn new valve when done. While letting it run the second event, I experienced the stalling when releasing clutch or engaging the mower. Now tonight when I got home, I turned on the valve cranked it about 10 times, got off and noticed about a 1/4 cup of oil had sprayed over the top of the mower deck and under the engine another 1/4 cup was laying below. I can't say where it's coming from. I then shut back off that new valve, dropped my head in disgust and walked away.... no patience left in me today to try and TS the seat switch possibility.

PS- Just went out to make sure the carb tubing was all intact and yes, it is. The appears to be spraying somewhere at the base of the engine onto the frame of the mower and down onto the drive and mower pulley. No gas in oil tonight, so I'm one step ahead of last night. ;-/

***" base of the engine onto the frame of the mower and down onto the drive and mower pulley."***
Well, that sounds like the sump gasket has broken, or blown out.
The stalling really does seem to be related to the seat switch. The fact that it dies when you either let out on the clutch.....or engage the PTO....is because the logic of the circuits considers the seat is empty and therefore kills the engine when you do either of those actions.

Getting in late, but thx again for the input Mownie. I will find the truth regarding the seat switch... sump gasket, yes, sounds like a possibility, nead to run the engine some more to know for sure, because I still haven't had it running since leaving the gas valve open. I turned her over about 10 revs. but the battery was getting low, then I saw the oil, it was another long day and , well, I just. gave. up. So I will report back after checking the seat switch and getting her warmed up again.

thx agin,
Mainiad