A common practice to plug holes in tanks is exactly what you saw. Drill out a small pin hole to make it clean, then plug it with a screw with a rubber washer or a bit of putty. In metal tanks, this works pretty good if the tank is stationary. A plastic tank that has flexing and movement, it's only a matter of time till it starts leaking again.
You said the tank was not full of water. Was the water above the screw or below them? If below, they probably still leak and the dealer is hiding that fact. Either way, you are probably looking at getting a new tank. I would not trust that one. INSIST they fill the tank all the way and put the system under a full load. If you are going to fork over $179,999 that's the least they can do for you.
Follow your gut. If you think the salesman is lying to you, he probably is. Its quite obvious he lied to you (or didn't know) about the batteries. You can't trust anything he says. Going forward, examine the coach on your own, without his commentary (and excuses). Then simply state what you want changed, fixed, or altered before you even consider buying. That's a LOT of money! That's more than my house cost!
Absolutely insist all tanks are full, and test all systems now! I have a feeling though, once you drive off the lot, you are on your own. You won't be getting support from these folks.
IRV2.com has a forum category specific for Monico. Maybe you can poke around there too:
Click here.
