1) The issue could be that you get not much air on low setting because it's low? Lots of noise on high means that's why there's a lower setting than high if you want it quieter? If it is air noise that is normal, though you might want to replace the cabin air filter and check for leaf/etc debris buildup in the intake. If the noise is more of a vibration or squealing then the motor might be worn.
2) Yes the line will condense moisture out of the air. Some vehicles have foam insulation over it. Maybe that one did too and it just came off. You could try putting foam on it and if it makes it run irregularly then take it back off. You can get 4 feet of foam plumbing tubing from a hardware store for $1 then secure it with nylon wire ties, or don't... if it's cold you don't really "need" to do that, it just increases efficiency a little and keeps water from dropping off onto the engine bay components (when parked, when driving the airflow probably dries it off).
3) Seller said this in response to you questioning 1) and 2) or for some other reason? No neither of those things indicates low refrigerant level. Short cycling of the A/C could, as well as inadequate cooling performance, or if the line was freezing up, literally frost forming on the outside of it when it isn't very cold out (and maybe not even then if it's external temperature regulated).
4) Per #1) above you probably don't need a new blower. They are usually mounted on the firewall towards the top, will be a circular plate, maybe 9" in diameter or so with the motor end sticking out as a roughly 3" diameter circular protrusion. You can look the part up on a site like www.rockauto.com
for your model year and engine to see pictures of it.
If the cabin air filter has never been replaced then I would go ahead and do that. None of these issues seem to be anything that should dissuade you from purchase, though if the seller thinks maybe the AC charge is low, you could try to argue for a few dollars lower selling price based on that belief, lol.