I'm an old RT guy. Never built a front wheel drive job but I've seen other guys do it and they work fine. Got an old Tri-Magnum that looks exactly like this one.
Tri-Magnums use a VW front end and you bolt any type of motorcycle frame to it. Had a 1500 Honda Goldwing at first, then a 650 Yamaha Turbo Seca 650. Valkyrie's are best because they have reverse. These things will out-corner a Corvette. That's not an opinion. It's been verified by Popular Mechanics magazine back in the 1980s. They are an absolute hoot to drive as contrasted with conventional trikes with one wheel in front which IMHO are suicide machines. RTs are super-stable, even more stable than cars. Don't turn over. Don't flip. Really. Why? All cars lift or go light on the inside rear wheel during hard cornering. Not so with an RT, which is glued like an MFer. No, they don't swap ends when they break free. The coefficient of friction is way up there. Anyone can learn to drive one well. I couldn't stop hootin' and hollerin' my first day in one.
This CRV set-up will kick ass. The problem with he smaller motorcycle engines is inadequate clutch area. No problem with the CRV. Length to width, you need 1.5 to 1.75 your wheelbase. That looks good. You can go a little longer - it's not critical. Weight distribution should be about the same on each wheel. The fuel tank should be towards the back of the seats where its influence is evenly distributed, not way back, because the weight changes. If you need to put more weight back there, use the battery and/or radiator. But you are sitting back pretty good in the CRV as is so it is probably close.
You're right to save aero for last. Weight reduction is the big thing. Put larger diameter, thin LRR tires on the front for better MPG numbers now that you're not pulling so much weight. Contis are real good. Same on the rear because you're not powering it. Use a hydraulic brake mixer sorta like the NASCAR guys use. You can hook up to your mechanical brake in back with a clutch slave cylinder. You'll just have to test it. An inline restricter will work for cheap but you can't adjust it on the fly for rain or dirt. You'll want something like 70-percent front, 30-percent rear applied force. This is real important. The rear brake keeps you straight. If you don't get it right, you'll flat-spot the rear tire or lose control during hard braking. Just take it out in the dirt first and stomp on the brakes, check your tracks, and set the adjustment to where nothing locks up. And you'll have to get used to checking the brake adjustment in back frequently.
I'm in California and we've always gotten away with registering our crazy stuff as motorcycles by welding that cylinder the forks attach to, with the VIN stamp, onto the rear frame and registering the vehicle as the motorcycle the frame belongs to. If there's any VIN numbers on the front part, like cars have, you have to take them off to show it's no longer a car and that stuff's just parts. Sometimes I had to try several DMVs to find someone with a sense of humor. But these days, sometimes you can run into trouble and try to get a special construction designation. You may need to find somebody who's drunk or on drugs. Good luck.