Complex sentence: Mr. Jingles, Del's mouse resurrected by John, is also still alive--but Paul believes his outliving all of his relatives and friends to be a punishment from God for having John executed, and wonders how long it will be before his own death.
Split into simpler sentences: Mr. Jingles, Del's mouse resurrected by John, is also still alive--but Paul believes his outliving all of his relatives and friends to be a punishment from God for having John executed. Paul is left wondering, if a mouse has remained alive for all this time, how long it will be before his own death.