Hi Blue Jays,
One caveat to the use low penetration loads for home defense. Remember that everything is relative. If a given load will not penetrate a sheatrock wall, something easily achieved with the human fist, how deeply will it penetrate a large male who might be wearing several outer garments? Will it penetrate deeply enough to do the necessary damage? Further, if the assailant dives behind a piece of furniture or television for cover, your shotgun will be rendered useless...at least until he decides to poke his head out. Walk through your house and look for specific points of cover that you could use if necessary. Pick prospective firing angles carefully. Do your homework ahead of time and you will have the best chance of survival in the end.
My Benelli Super 90 is loaded with Winchester Premium #1 Magnum buckshot (20 copper plated 0.30 pellets). This buffered load shoots very well in all of my shotguns.
For street us, I keep some Winchester Premium 00 Magnum buckshot on hand. For long range shots Winchester one ounce Forester slugs.
This is not a blanket recommendation for Winchester. These are the loads that shoot best in my gun. Winchester is also very plentiful in my area...so that makes it a win-win situation for me. I'd stick with Winchester and Federal though as they seem to have the best quality control.
With respect to spring compression, the problem is most common with autoloading shotguns which rely on perfet spring and ammo performance for proper functioning. Pump guns are far less sensitive. Case in point, I have an old Winchester 1300 Defender in my trunk that has been loaded to full capacity with the same spring for nine years and it has yet to miss a beat at the range.Springs are cheap enough to buy several so you can install a new one from time to time.
As others have said, try some different loads and see what your gun likes.
Get the Sidesaddle and Speedfeed stock. The more rounds on the gun the better as it is probably all you will have time to grab in an emergency. I like to keep my Benelli with the chamber empty, #1 buckshot in the magazine, and slugs on the Sidesaddle. If the BG is still running around after a few blasts of #1 buck, it's time for a slug to dig him out.