sorry to hear about your situation, but lets break down your first part about wanting the dude to suffer.
chances are if you shot him in the head and he lived for 3-4 days, he wasnt conscious and probably felt no pain at all. just lights went out and involuntary and machines were still keeping him alive. So he lives on machines for 3 days, taking time and resources in a hospital bill that is 100% paid for by the tax payers.
you want to use a 25 acp? why? you only get one shot and if you dont kill the guy and he lives, you are in jail and he is locked up too with no chance for you to finish him off.
No, the DRT option is the best in the Plauche situation.