I have a 7 yr old house and our outside faucets have backflow devices attached to them. As I was removing the hose off for winter prep, the backflow device came off as well. The problem is that when it was previously assembled, they used rubber cement like substance to keep the device on.

My problem is this, my threads are no longer working (I even used a wire brush to clean the threading) and now my outside faucet is useless. I would like to replace the faucet but it is unscrewable as the faucet is attached inside the exterior wall, so I am afraid to overtork it and cause more severe damage. We have a brick home if that will help any.

On a side note, it seems the threads on the current faucet have thinner gaps between them than a normal water outlet would have, if that makes any sense. Any help would be appreciated.

The backfow preventer are held on to the faucet with set screws. If you didn't remove the screw, you may have stripped the faucet threads. To the best of my knowledge, all outside faucet threads are the same thread. A possible solution is the epoxy a brass hose repair fittingn to the old faucet. There is usually enough grab to set the barb inside the old faucet but trimming is usually needed. I have do this using JB weld and it works well. Another solution would be tp try and epoxy the backlow preventer over the old faucet. See if the set screw can be tightened or possibly replaced. Tey are not expensive to replace.

Assuming that you are talking about the type of back flow preventer that screws onto a hose bib, I believe but do not know for sure, that the back flow preventer is designed to distort the screws as it is installed. Thus preventing removal. While a hose may not screw onto the hose bib, another back flow valve might.
Depending on the type of pipe you have, the hose bib may be solder on not screwed on. If so, that would certainly make replacing it an inside job.