If the gun will really be used to protect your life, don't cut corners. In a high risk/high stress environment short stroking a pump is a real concern for the uninitiated, and your comment concerning alack of training rounds is a red flag.
The two solution I have to offer is to choose a SXS double or a reliable semi-auto of the Benelli class. The double provides a short compact gun that is mechanically simple and extremely reliable, particularly if its the exposed hammer/double trigger style. The Benelli offers greater firepower, but has an advantage in that if you needed to switch loads in the middle of a conflict, it could be done without taking the gun out if action, thanks to it's cartridge drop lever.
If for example you were loaded with birdshot and needed to switch to a slug, you would simply trap the slug load between the fingers of your support hand, and the forend, pull back the operating handle with your shooting hand, slide your support hand back towards the ejection port until the slug load enters the receiver, release the bolt handle and fire. No subsequent round from the magazine would be released unless the cartridge drop lever was hit.
If you're set on a pump gun, the Mossberg 590 is the top choice IMHO. I've carried mine for 12 years now, and its never had a single hiccup. Nothing has worn out, but should it, there is nothing on the gun that cannot be replaced by the owner. The same cannot be said for Remingtons as they gain experience, due to their stabbed in cartridge stops, and riveted ejectors.