1. These days, everybody seems to complain about economy class service on all airlines, so you're probably best off trying for a plane that has PTVs (like a 777). If alcohol is a big deal, the European airlines in Skyteam don't charge for beer or wine; the US airlines do. In any case, you'll have to connect in a hub like ATL, EWR or DTW or at least a major gateway like JFK. I would want to do this with a minimum of connections, so your domestic flight to the international gateway would be a factor. You can mix and match airlines on any given itinerrary
3. In my experience, AF has the best award availability for first and business but you want economy so I'm not sure if that applies. AFAIK, the only difference is on the "home" airline. In other words, DL's availability for AF should be the same as CO's but DL should have extra seats for DL SkyMiles members (not just elites). At least this was true when I tried to book a NW ticket on CO where CO was showing availability for a certain flight but NW wasn't.
2. You pretty much have to do it the way you've outlined it here. No easier way that I know of unless you want to pay to use WebFlyer's AwardPlanner service.