Don't do it!
Unless your life's partner (How was that for inoffensive?) is willing to commit to your dream and make it her own, it's never going to work out for you. I tried this with my wife of 30 years. She soon became my ex-wife.
Sounds like you folks might benefit from taking a crewed charter for a week or two to shake out the sea legs and determine if mal de mer is going to be a problem for your wife. Don't invest in a new boat until you get this deal breaker figured out.
If you determine that the ocean's going to remain a dream and not become a reality, gas up the RV and get moving! There is no end to the beautiful places you can discover while driving around the back roads of North America.
Good advice. Make the charter in the prettiest place you can find, and bring along ginger, bonine, whatever your seasickness remedy of choice is. Look at somewhat bigger boats than you're current one - living aboard long-term won't work if it feels like camping out and its hard to fit many creature comforts in a boat < 30-ish feet.
Don't focus on what you're giving up (like a house, garden, big-screen tv, whatever) focus on what you gain - freedom, interesting experiences, sunsets, NO SNOW. We just began our 8th year living on a 33-ft boat, currently in the Bahamas out islands.