Craftsman 21hp mower model# 247.28885 quit running.

So, I was 3/4 finished mowing my lawn when all the sudden I noticed an audible change in the sound of my engine. It sounded like it was clogged w grass or it was choking down or perhaps a compression issue. Shortly thereafter, the mower cut off.

Since then I have not been able to get it to run. It is very hard to turn over. I have replaced battery, checked all the safety switches, removed n cleaned the carburetor, removed old gas, bought n put new gas, checked the gas cap, checked the solenoid, blew out the air filter, replaced the spark plug. I removed n grounded the plug n it gets a good spark. The engine turns over easily when plug is removed as well. This tells me the plug, solenoid n battery are good. I took off air cleaner n tube n sprayed starter fluid directly into the carb. I got it to start but it ran very rough so I cut it quickly off. Seemed like a compression issue so I followed YouTube video to check valve adjustment. Upon inspection, valves were very loose. So much in fact, the metal cap on the end of the rod had fallen off. I adjusted valves as per video to .004 on both. I tried to start mower but it is still not starting and very hard to turn over. I'm open to suggestions at this point...