Personally, I would not use any gun for self defense that was so weak, or I was so concerned about damaging that I couldn't load it with high performance ammo.
Secondly, I would not trust my life to weak and ineffective loads.
Your question baffles me. What is more important to you, the gun or your life?
My 38 Special carry load is a 125 JHP at a clocked 1,200 FPS from a 2" barrel. I feel OK with that. I consider mainstream "+P" (125@925 from a 4" barrel and around 900 from a 2" gun) to be much too weak to bet my life on it. You want to go weaker than this? To avoid wear on your Detective Special? I go back to my previous question, which is more important to you?
The DS is real cool and all, but maybe you should consider a more utilitarian pistol as a working gun? Seems like you want to treat it as a collector's piece rather than a practical carry gun.
PS: Why do you think your Colt can't handle +P ammo? I suggest shooting 5,000 rounds of mainstream +P and see what it does to the gun. By the way, the answer is it will do nothing. Your DS was designed to handle loads at 21,500 PSI. Current "+P" runs 18,500-20,000, or well below maximum allowable pressure. Why the concern?