You've got the right idea on the first part of your route. However you leave Delaware or Assateague, you'll find your way to the Chesapeake Bay Bridge on Routes 50/301. On the other (west) side of the bay, you'll stay on 50 to I-97 north, to MD 32 west. As you said, that will take to to I-70 at West Friendship. (It's the easiest way in an RV, trust me, I've tried every route.)
From there, you could stay on I-70 the whole way to St. Louis if you want, though I prefer to get on I-68 at Hancock, MD, then I-79 north at Morgantown, WV, back to I-70 in PA. (Avoids the PA Turnpike.) As you say, you could do Rocky Gap in MD, or (my preference) Deep Creek Lake (stay in the state park campground). The rest of I-70 isn't very scenic, though there's the Columbus Zoo and the museum at Wright-Patterson AFB, for starters.
An alternative we've tried is to take I-79 south instead at Morgantown, then pick up I-64 west at Charleston, WV. A much prettier route, to me, though it takes a bit longer.
Good luck, and enjoy the trip!
Make sure you check the routes you plan to take ahead of time. There are a number of restrictions, mostly based on size. If I recall correctly, you can't drive a motorhome that size in D.C. at all (not that you'd want to). You also can't drive on the George Washington Parkway along the Virginia side of the Potomac (low underpasses), nor through the interstate tunnels under Baltimore Harbor if you have propane (though I heard this might have changed).
Keep in mind a lot of sellers and dealers of used DPs like to use MSRP as an original starting point. From what I've seen poking around, the actual sale price is substantially below that. It seems paying somewhat around 70% of MSRP is common for a new DP.
Yup -- I was going to say the same thing. It's easy to get 25-35% off a new RV, so any depreciation has to start from there. But as others have said, what's the point? Buying or selling, the used value is whatever the market will bear.
I've used the truck stop DEF pumps once or twice, but even though my DEF fill is on the driver's side, it's so far back that I have to pull up partway after filling the diesel tank. So I mostly use the Blue DEF "boxes" from Wal-Mart, and generally add one (2-1/2 gallons) for each fill-up (usually around 90-100 gallons in my 150-gallon tank). That ratio seems to work out about right. I track my fuel use carefully, but haven't bothered to monitor my DEF usage any closer than this.
I believe Aqua-Hot (and others) will tell you to use the pink stuff, because the blow-out method won't guarantee that the fresh water coils inside the AH are totally free of water. I'm not sure I buy that, but the price of being wrong would be very high if the unit froze up.
To me, the pink stuff is cheap insurance. I've never had a problem with after-taste -- just open the low point drains, then flush and flush and flush. If you leave any pink hiding in the system (like in stub lines to washer, etc.), it will keep mixing in and showing up.
We have a 2014 CR-V, and had the battery run down the first couple of times we towed. (I tried following the directions in the manual, but they told me to pull the wrong fuse.) I plan to have a charge line installed one of these days, but in the meantime, I just disconnect the positive battery cable as the last part of my hookup. Adds about 30 seconds.
We have a 2014 Tuscany, with no major problems in 1-1/2 years and 15k miles. Ours has one hydraulic full-wall slide, and two shorter slides with Schwintek mechanisms. The only consistent problems I've heard of with the Schwinteks have been on full-wall slides, which plagued the earlier Thor Palazzos. The problems may or may not have been largely resolved by now, using upgraded Schwintek hardware (stronger motors, steel vs. aluminum rods, and/or three tracks instead of two).
At any rate, I've yet to hear of related problems with the Tuscany slides. The Tuscany isn't a perfect coach (if such a thing exists), but it has a lot of good features for the price, and for us, the floor plan that we liked the best.
I have a 2-macerating-toilet setup like you describe, but wouldn't try to do a gravity dump through a 3/4 inch hose. While the toilets "liquefy" everything quite well (no poop pyramid, for sure), as that stuff sits in the black tank, the solids still settle, so that the first part of your drainage is going to be a pretty thick soup. I use the good old stinky slinky, and it dumps quickly and thoroughly. Then I do the gray tank dump, then run my tank flushing system (if I'm packing up to leave), with a clear adapter so I can see the progress. It certainly drains, and cleans, more quickly and thoroughly than my previous non-macerating units.
Interesting responses indeed. No one has mentioned the only type of "financial advisor" I have ever used (and ever would), which is the type that charges an hourly fee for their time and expertise, and takes no commission or kickback on their recommendations. That's who we hired to look at our overall picture before we retired -- cost us a thousand bucks or so, well-spent in my opinion, for a truly objective look at our then-current and future finances. I can't trust an "advisor" (usually a stockbroker or insurance/annuity salesman) who makes money on the products he advises me to buy -- he has a built-in conflict of interest between what's best for me and what's best for him.