Can't answer any of your questions but do feel like I know you, now, as well
Good luck in finding the right boat for you and your family. We looked almost exclusively at ketch rigged boats with a few yawls and schooners thrown in. We ended up with the purchase of a schooner (that we're re-buidling/re-fitting right now). I must say that ketches really vary in performance and ability to sail short-handed. You really need to get out there on the particular boat and check it out.
Here's a bit of info about the Gulfstar 50 that I just found via Google. You probably have already seen it. link
The only Gulfstar 50 that I've seen was center cockpit (I guess they all are?) and ketch rigged with a smaller mizzen than I like on a ketch. My favorite set up is for main and mizzen (on ketch) or main and fore (on schooner) to be close in mast height/sail area. I believe it is most versatile. However, the Gulfstar 50 I saw had such a large main that one would lose a bit of an advantage of split rig (smaller sail sizes). Have you sailed one yet? How is it?
Assuming that you have sailed a bit (since your wife has not...) regarding your wife and sailing--if she's game (and you're not pushing her to be game...) it will all work out. If she's humoring you (loves ya, wants what you want...) beware. Both my husband and I really wanted to sail and cruise. We worked on making a plan and making our "new" life together--equal partners in all efforts towards the goal. We're had many, many, (MANY) male sailing friends who discovered that their wives were simply agreeable and trying to make everything work out--until it didn't.
We don't have children, but think that if we did we'd have taken off long ago for a cruising life because we both believe that home schooling and travel are a wonderful way for kids to grow up.
Best of luck to you!