You are asking whether you need a fusion for lower back pain. The answer is that it depends upon the cause of your lower back pain. Degenerative disc disease can be quite painful and possibly you could need a fusion to relieve your pain.
Have you had a conservative treatment? This includes medications and injections (epidurals)? I assume that you have a strong core so PT might not be necessary.
Have you had a workup? This means possible facet blocks and/or a discogram? Depending upon your examination findings, it might be that the facets are causing your pain and you do not need a fusion but need rhizotomies (see website). If there is more than one disc that is degenerative, you might need a discogram to make sure this lower disc is the painful disc.
A lumber fusion are generally very good for pain relief in the right patient. I am a bit worried that you plan to go back to squats and dead lifts as these actions place tremendous sheer forces on the discs. In my opinion, these actions should be avoided in your case.