1. I am pulling a ... Trailer. rack and paniers on back of bike, lowriders on front. paniers will be light, heavy stuff in trailer. I will be carrying a load appropariate for this trip - about 1900 miles when taking expressways, longer by back roads though I dont have the route planned yet. see #2 below. -- For a 1900 mile trip, you can easily get away with one set of panniers, a trunk bag, and a handlebar bag. I rode 5000 kms (3000 miles) over 3 months in Australia with that much.
Just remember, if you are planning to spend any time in a hostel/motel/hotel you have to carry all that up to your room. If you plan to do a section by train or bus, you have to carry all that around the station. And when go to fly back, you've got luggage weight restrictions to deal with, plus you've got to carry all that stuff around the airport. Also ... considering that most airlines have a 2 pieces of checked baggage limit, how do you plan to bring all that back with you? Have you read your airline's bicycle and baggage policies yet?
2. how do you recommend planning the route - are there available resource showing best cycling routes> just use google? need to plan stop so they are at campgrounds, what is the best way to do that? -- I usually get a map (a physical, paper map) put it in my map case on my handlebar bag, pick a road that doesn't look like it will be too busy, and ride. BTW - if you want a somewhat flatter route, you can usually (but not always, no guarantees) find it if you pick a route along a river.
3. have been purchasing gear using recommendations from this forum. very helpful, thanks. using a summer weightdown bag, prolite 4 pad, dragonfly stove, MSR raingear. -- Don't forget to check the weather in Michigan ... they are going into the fall season now and nights could be chilly.
4. biking tights or shorts with biking pad underwear? issues and pros and cons? -- Cycling shorts with basketball shorts over them.
5. average miles per day goal? 50?? I plan on a day off about every 5 days or so. -- Whatever YOU want!
My Australia tour nearly killed me with the distances we were doing, and the terrain we were covering, but the European tour I just finished was much nicer and we were doing only about 60-70 kms a day.
6. condition - currently 210 pounds, could lose some. plenty even. I can ride back to back centuries here in SE mI a week apart - ride 60-70 miles the day after a centory no problem. have been doing about 200 miles a week sometimes 280 for about 2 months now. can i do this? -- Just an incidental terminology comment ... back to back centuries are centuries on consecutive days i.e. one on a Saturday and one on a Sunday. But back to your question, yes, you sound fit enough, and again, ride distances each day that you feel comfortable with. Touring is not racing or randonneuring. You don't win anything if you complete a certain distance each day.
7. allot what duration of time for this? a month? is that too agressive? how much? (one way time, I am flying back) -- Use math. If you are comfortable with 50 miles a day for 4 days then one day off, that's 200 miles every 5 days.
8. time of year - plan to start end of next week, or at least by sept 17. should be ok provided I corss rockies during a good weather window? -- The earlier the better when crossing the Rockies. Up here in Canada, already I'd be saying to expect at least some snow in the Rockies, but I'm not sure how it is in the US.