Boozer - smart of you to ask for input on wheels for clydes, and the advice above is solid. Seth in particular knows his stuff when it comes to wheels and I absolutely agree with his recommendation to go no lower than 32 spokes per wheel.

Thinking broader, make sure you ask the same capability question of the rest of the bike. The Synapse Carbon Disc is an awesome bike but appears to be rated at 275 lbs for the rider and 285 lbs for rider+cargo. See page 53 of Cannondale owner's manual: Mountain Bikes, Road Bikes, E-Bikes - Cannondale Bicycles

I've found that a lot of the full carbon bikes have similar or even lesser load restrictions. Specialized introduced the Roubaix with Future Shock technology and it's been a big hit but behind the scenes they have quietly lowered to the max weight recommendation from 275 lbs (for most models) to 240 lbs for all Roubaix models 2018 and forward. You'll need to do a fair amount of digging to find max weight recommendations on bikes; manufacturers tend to bury that info in the manuals and not advertise it. There is a lot of debate out there about clydes on carbon frames; certainly it's better than being on a very cheap store-bought aluminum frame but on the other end a clyde may feel harshness to a carbon frame that a lighter rider would not.

IMHO, spending $3k for full carbon on your first road bike may not be the best move. Even though your FX3 is a nice solid bike, you're going to go through a learning & growth curve with any decent road bike and a year from now you'll be a different rider. You may be better off sticking with a metal frame (alum or steel) and spending the money on upgraded components like groupset (105 or above), wheelsets like described above, disc brakes with at least 160mm rotors, upgraded tires, etc. You'll get a great bike that will serve you well as you grow & learn and you won't have to worry about nicking up a carbon frame. After a couple of years of riding a road bike you'll have a better idea of what works for you and then you can go carbon, steel, titanium, etc. The alloy version of that Synapse (with carbon fork, 105 groupset, etc) is about $1400 less; you could do a lot with that difference.

As I tell the other clydes in my riding group, if I was that concerned about the weight difference between a carbon frame and a good alloy frame, the smartest thing I could do is skip lunch before riding.
Good luck bike hunting!