I decided NOT to buy this car, but wanted to know what might be wrong.

1986 244 DL with 5 speed manual, non-turbo, 213k+ miles (odometer doesn't work). Many minor issues (rust bubbles in quarter panel, small dent on trunk, no radio, no overdrive [I presume it just needed a new relay]). Independently confirmed license plate and it passed smog on DMV's website. No leaks visible. Coolant quality was halfway up coolant tester. Oil and PS fluid were clear/newly changed. Coolant pressure tested okay. Initial red flag was clutch pedal on right side was VERY worn, making me think the clutch was used a lot, e.g. city driving and/or misused. Of course, no records for this car were available.

There was minimal (1/2"?) movement left-right in the shifting stick. My old Volvo had 2-3 inches.

On starting engine, I heard a constant rumbling/humming noise that went away when I completely depressed the clutch. I reproduced this several times.

I heard a single slapping noise toward passenger side on shifting into second gear. I reproduced this.

The car was loud on shifting into 3rd and 4th, but quiet when I took it out of gear.

The engine died only when releasing the clutch when the clutch was close to the top.

No stumbling when driving. No popping out of gear.

I called a mechanic, who said the clutch needs replacement and a front bearing caused the rumbling/humming noise that stopped when clutch depressed. He warned that an internal issue with the transmission could be at fault for this rumbling/humming, which puzzles me.

The ultimate deal killer was dealer/flipper shrugged his shoulders and made a face when I pointed out these facts to him. He said the car is cheaply priced and "as is." I was upset, because I called him before going there and he said NOTHING about the clutch or transmission. He's not completely ignorant, because he explained reverse on this car and said the car's just quirky with a narrow left-right play in the shifting stick.

What are all the causes and most likely cause of:
narrow neutral position for stick?
rumbling/humming on idle that stops when clutch depressed?
slapping noise?
clutch release killing the engine almost near the top?