I'm sorry to hear of this with Murphy. I'm afraid that the history you've posted is quite worrisome for reasonable return to function. Here's what you need to know:
The most important prognostic indicator for paralyzed dogs - usually due to degenerative disk disease in a 10 year old bulldog - is the presence or absence of nociception (deep pain). This assessment is always subjective but apparent loss of sensation caudal (toward the tail) to the level of spinal cord injury suggests the possibility for permanent paralysis regardless of treatment. Approximately 50% of dogs in this condition recover if treated with decompressive surgery.
Approximately 90-97% of dogs with intact nociception, even if they're paraplegic or tetraplegic, recover fully or nearly fully with surgical decompression. However, the time frame for recovery is extremely variable (few days to many months).
With nonsurgical treatment about 85% of ambulatory and 50% of nonambulatory (but retaining pain perception) dogs ultimately recover.
The recurrence rate (i.e., a new disk extrusion at a different level) is low in nonchondrodystrophic breeds (non "pushed-in faces" breeds), although some of these dogs (especially German shepherds) may have initial signs attributable to disk disease at multiple levels simultaneously. For chondrodysplastic breeds treated with surgical decompression, recurrence rates vary from 5-20%. The recurrence rate for medically managed patients is about 40%.
Dogs with signs attributable to ascending-descending myelomalacia due to bleeding in the spinal cord have a poor prognosis. Murphy's vet needs to assess Murphy's nociception in order for you to know what to expect with Murphy. Unfortunately, his urinary incontinence and anorexia only compound the extensive husbandry needed to support these dogs while they're recovering if, indeed, they can recover. Please respond with further questions or concerns if you wish. I have to leave my computer for 15. hours but promise to reply when I return if need be.