Welcome tacomancini!
You can also try to cut out a bit from the rubber circle that is between the sprocket & the spokes - cut off maybe 1/3" from the inner side of the circle and re-mount the sprocket, this will let the sprocket come a bit closer to the spokes. If it still isn't enough then go ahead and bend the fork out a little and stick some washers on the axle. If you really want to make the "rag joint sprocket clamp" permanent/strong then goop everything up with urethane windshield adhesive before you tighten it down, I guarantee that it will never move on you if you do that ;-)
Don't worry about wheel alignment (rear relative to front) not being perfect, even if the bike tracks a bit "off" it will be barely noticeable. Sprocket alignment on the motor drive is the important part, make sure everything lines up there.
I'd recommend keeping the multi speed wheel, lets you choose a gear to start the bike with, also you dont have to worry about tightening the pedal side chain thanks to the derailler.
Dilly Bar Rob