I just listen to your video, I don't hear anything I would be alarmed about
As far as the condensation and residue on the floor behind the car from it being started and allowed to run in place I wouldn't be alarmed
How old is the gas in the car? The reason I ask that is when cars sit for long periods of time condensation occurs in everything hollow part of the vehicle including the brakes, gas tank, engine, exhaust system and tranny even when stored in a garage
Letting cars sit for long periods of time is hard on them, way better to drive them regularly long enough to get all the fluids hot enough to evaporate all the condensation out of the engine and drive train Starting them up every 30 to 90 days and letting them run in neutral or park for 10 to 30 minutes is a big NO NO in my book
EDITED. Do the mechanical tests suggested first before doing anything else Compression and leak down both cold and hot as well as look real hard at the spark plugs and let us know your results