Hopefully somebody with insurance knowledge will chime in. With your house being that age, check and see if there are any other newer homes further(uphill/altitude) up from you, that may tie into you sewer system. Those newer homes may help overload the sewer system, and have been overlooked by governing officials. You might be able to get an idea with Google earth. Moving the cursor the cursor will give you somewhat of an idea on altitude(bottom of screen),yours plus other newer homes above your home. They have storms all the time, that they measure in rainfall inches per hour, and for a time length I believe (something like that). Your home hasn't been around long enough to find out, unless it was built in a neighborhood that was there a lot longer. A lot of areas have laws that say you can't have a footer drain run into the sewer system. That helps, but the right storm will overload the footers sump pump, cause that water to run over into the sanitary sewer, overloading it. When a storm like that comes along, you could end up with raw sewage in your basement. The correct insurance is all you have left, to my knowledge. Definitely make sure what you have covers sewer backup, and anything else they may call it.
Music Room and Floods
I am in the process of buying a new house that will have a dedicated music room in a look out basement. This house is 14 years old and the basement is finished. the music room is 21x16. This is not in a flood area and has never had any water seepage or other issues. It has a sump pump if needed. I was surprised to find out that in the case of a flooded basement there is not much coverage for my audio system. Anyone have this issue, any ideas. I will get the sump pump checked, have a battery backup installed but would appreciate anyone elses thoughts or experience.