I definitely agree with you it makes sense to target Americans rather than Belgians. As you say, there are more people with much higher travel budgets, even if they are much further away.
Definitely research your competition! Trek Travel was mentioned above. Other high-end companies, in decreasing order of price, are Butterfield & Robinson, Backroads Travel, and VBT. Most of these involve luxury hotels and multiple guides for a groups of 10-20 people, with a support van or two, and can run up to $1000/person/day. You are probably not proposing an ultra-luxury trip, but it still makes sense to look at what is on offer at the high end for inspiration, and to know when you can match their offerings and when you can't. I believe all provide detailed itineraries, like 10 page PDFS (some might be "by request", meaning they want you to give them your email so they can add you to their email marketing list), so you can get a very good idea of what they are doing. I don't think any of these are gravel riding so you won't be looking at them for bike routes, rather at what sort of non-biking activities they include.
Meanwhile, you should also figure out what your target cost will be for the trip and find other companies in that price range. And maybe even search for gravel tours specifically as well. For instance I just googled "guided italy gravel bike tours" and found a
Tuscany - Strade Bianche Explorer Guided Gravel Riding Tour from Saddle Skedaddle Cycling Tours.
Figure out what will differentiate your tours from those other operators. Is it your local expertise, your unique routes, your prices, your advertising, your high quality bike rentals?
Definitely figure out whether there will be any support vehicles, the number of guides, how often you'll be moving lodgings, how the luggage will get from one place to other, how you'll offer rental bikes to those not bringing their own, etc.
For my own part, thanks to my parents' high travel budget, I've been on 3 guided trips with Backroads as a kid/teen. They were all "multisport" trips, meaning a mix of hiking, cycling, and other stuff like kayking, glacial lagoon tour in an inflatable Zodiac, etc. As an adult I have looked into how to approximate a similar experience with a different tour company so as to avoid paying Backroads' prices, but I haven't done any of those trips. I love your idea of combining biking with culinary experiences. I would say, if you want to provide half board, consider providing breakfast and dinner, leaving lunch up to the guests. If a ride spans over the lunch hour, guests could stop in whatever picturesque Italian village they're passing through, whenever they are looking for a break. Then after the day's outings everyone will be back at the hotel and can eat together as a group.
Keep us posted on your thinking and efforts!