Hi,
I think the FX3 is absolutely worth the price premium. For your $220, you get a carbon fiber fork (vs. aluminum alloy), a pretty nice 9-speed drivetrain (vs. entry level 8-speed), IsoZone handlebars and grips (vs. standard solid grips), and Shimano hydraulic brakes (vs. Tektro hydraulic brakes). I think those are worth the additional cost, and you'd never be able to buy those parts and upgrade for $220.
I think the $210 difference between the Coda Sport and the Coda Comp is an even better upgrade than FX2 to FX3 (for the value you get). The Coda Sport is truly a high quality bike...full Reynolds 520 double-butted frame with carbon fiber fork (vs. double butted steel frame and fork on Sport), and Tektro hydraulic disc brakes (vs. linear pull rim brakes). The Coda Comp's drivetrain (8-speed) is similar to that of the Trek FX2...with the Jamis, you're paying for that high quality steel frame. Both Sport (27.0 pounds) and Comp (26.5 pounds) will be competitive with the FX bikes in terms of weight.
They'll likely have very different feels to you, though. A steel frame will probably feel more comfortable, and more flexy, than an aluminum frame. I have a similar bike to the Jamis Coda line -- an older Trek 750. It's a '90s touring/hybrid bike with a double butted True Temper steel frame, and it definitely feels more compliant than a modern aluminum rigid hybrid. You may like that or not; I would certainly recommend trying all of these to see how they feel to you.
My last recommendation is tire clearance. With your intended riding, I would recommend larger tires, and the models you're looking at will likely support up to about 40mm tires. For your riding, I like something like a Giant ToughRoad (rigid 29er hybrid) or Giant Roam (29er hybrid with a suspension fork). The Giant ToughRoad is pretty unique, but the Roam is basically the same as a Trek DS, a Specialized CrossTrail, Jamis DXT, etc. The ToughRoad comes with 2" tires, and I know you can fit 2" tires on the Roam and DS bikes. For mulch, gravel, and riding on sand, you'll want a larger tire footprint. It needn't be a knobby tire -- there are plenty of 2" tires with smooth tread patterns for use on pavement -- but I think you'll want that wider contact patch for the softer surfaces you're considering. As an example, I have the 29x2" Schwalbe Hurricane on my Roam. It's a pretty soft and compliant tire and, with the right inflation, it just floats over any sort of gravel surface or trail you want to ride.