The results from the Kansas lab -- it is absolutely necessary to have to ORIGINAL paperwork, and in fact, it has to be taken to the USDA vet -- right?
Yes, you will know that it is the original form because it will have a sticker on it with the results. The rest of the form will likely look like a photocopy, but the physical sticker proves it was the real deal from KS. You need to bring that, the rabies certificate, and the EC 998 form to the USDA vet for endorsement. (You can probably also mail this in, but that will depend on the USDA vet for your state.)
No answer given on what happens if I can't do the USDA step until (shortly) after the 6-month frame from blood draw. And another question on this one ... do I actually take my dog to the USDA vet? I assume yes...
You don't take your dog, just the forms. As long as 1) the rabies vaccination date is prior to the blood draw date 2) the rabies expiry date is in the future, you're fine, even if the blood work happened more than 6 months ago. If the rabies vaccine is set to expire before you travel, you can get a new vaccination done and include both certificates in your paperwork and that is fine (just make sure to have the microchip # on both certificates).
It's okay if my vet just signs the EC 998 form in the appropriate places; it's the USDA stamp / sticker that is required -- sounds a little iffy on this one??
I can check when I get home, but I think my vet's "stamp" was just their standard "___ Vet Hospital, __ Street, City, State" one, it wasn't anything more official. My vet also signed/dated the form. The USDA did stamp the date on the form with their endorsement, which is what starts the 4-month window for travel.
Perhaps one of the most important to me -- sounded like some conflicting thoughts on whether I could send my dog to Heathrow early and have my wife pick her up. Maybe if both our names are on the info? And the EC 998 form is only in my name ... by "info" I'm hoping that means whatever paperwork I do for the airline?
I flew my dog/cat via BA from Dulles -> Heathrow in April. My mom dropped my boys off at Dulles and I picked them up at Heathrow, so that should be fine. I had to fax a form to James Cargo (the agent BA uses at Heathrow), and I believe that included my contact info (as the person picking up the animals). There was no problem about different people doing the dropping off/picking up, but there was also no notification. (I imagine if I'd been running horribly late or something, they would have called, but I arrived about 30min before my boys got off the plane, so there was no need to phone.) The flight landed at 9:15am and I arrived at Heathrow ARC at 10am, and walked out with the boys about 11am, so provided your wife arrives in good time, it should be fine.
I don't know if someone addressed it, but in answer to your "if travel doesn't happen in the 4 months" question, you would need to re-fill out the EC 998 form and get the new one endorsed by the USDA vet, which would give you a new 4-month window. Shouldn't be an issue, though, since you don't have to do the USDA endorsement the minute the 6 month waiting period ends, so you can plan to have the 4-month window be when you plan to travel.
Good luck!