Most of my doubts about his healing ability were answered here.
Deadpool has one of the greatest healing factors in the Marvel universe. As mentioned here:
Deadpool possesses a superhuman healing factor derived from that of the mutant Wolverine that allows him to regenerate damaged or destroyed areas of his cellular structure at a rate far greater than that of an ordinary human. As such, he can regrow severed limbs or vital organs.
However, I have a slight confusion about Deadpool's regenerative limit. What is the deciding factor which chooses to grow into a complete 'Pool? Hypothetically, for example, if he's blasted into several pieces, will we have multiple 'Pools? (that would be fun though!)