Holy Cow Mamma.... If I were you I would get that thing out of there asap! And I wouldn't fool around w/implants either. It's in the very back and will not show. Teeth typically shift forward if they are going to shift at all. It sounds like you have dealt w/this thing long enough. IMO, it is a ticking time bomb and you don't know when it's going to explode. I wouldn't want an infection like that in my head. Then add ttc to the mix.... no way! Get that out and give your body time to heal (it won't take long once that thing is out of there) and then ttc again... worry free of that nasty thing.
I am speaking from experience. Back molar, multiple problems and infection. I even tried the root canal knowing the side effects/issues and in the end I had to get the darn thing out anyway. Best thing I ever did! I did not do any antibiotics. After the failed root canal, I was told that if I got the tooth out right away that I wouldn't need them. Find a good specialist/oral surgeon w/lots of experience. Seriously, life is too short to have to go on dealing with this.
I wish you much healing.
All natural sahm to dd1(12yo) and dd2(6yo). Married 16 years.
Time for the Master Tonic!