You're well on your way to making your next thread called "My Wheel Adapter Failed!". That's a death trap as is, DO NOT drive like either of the two examples shown.
You need the lug nuts that hold the adapter to the hub that will sit all the way recessed. Any reputable manufacturer of adapters or spacers includes proper lug nuts to do such a thing. If yours didn't, then call them.
And, no, putting it in 4wd with three tires on the ground won't help unless you have a locker in that axle. You could get someone to hold the brakes while you tighten them up, or if it's the rear you can set the parking brake.