Since there is no national registration and most U.S. states don't require registration, it's very difficult to say the exact number. Estimates range from about 180 million to about 300 million, depending on who you ask.
No one source of information.
Impossible to answer without knowing what you mean by illegal handguns.
There are millions every year.
No
Yes, they are.
No exact answer, as there is no exact record- a good estimate is about 120 million privately owned handguns in the US.
that particular category of death is not tracked.
Many different brands.. Too many to list by model. Popular brands which manufacture handguns in the US include Springfield Armory, Ruger, Colt, Smith & Wesson, Kimber, Les Bauer, and others.
The most current year that data is available for is 2005. In that year, US manufacturers produced 1,088,827 handguns. Not quite 3,000 per day. That does not count handguns that are made outside the US and imported. Nor does it count handguns that are legally made by a private citizen for their own use, nor black powder type firearms.
In the US, yes.
Fail to understand the "so called" part of your question. Yes, handguns made in other nations are imported into the US by a Federally licensed importer.
Since most states don't require registration, and there is no federal law requiring registration, most of the handguns in the U.S. are unregistered. "Unregistered" is a misleading term. It implies that a person has failed to do something that is required.