I would suggest that you look into political organizations that support what the Democrats say. Wikipedia has a list of pro-gun control lobbies that you can further research. Off the top of my head there is the "Brady Campaign" which was named after Ronald Reagan's press secretary who suffered brain damage from a bullet fired during the Reagan assassination attempt.
I would also recommend Wikipedia's "Gun Culture in the United States" article which lists a neutral-ish stance of both sides of the issues.
I would also recommend looking at the historical arguments around the 2nd amendment including what the language of the time meant as well as the relevant Federalist Papers (#46 I believe talks exclusively about the Framer's opinions on why they thought the Second Amendment was necessary).
I would also recommend looking into the pro-gun rights side, as you seem to grasp some of the nebulous tenets, but not the basics of the argument (i.e. either you are not convinced by the Republican position OR you are not fully informed).
As further advice, I would double check any numbers that are not listed as "per capita" (per capita is usually "100,000 people" in gun statistics). Some sites will do per million or per 100. These are okay, but per hundred thousand is most commonly used. For all numbers that are per million, divide by 10. For all numbers that are per 100, multiply by 1,000. For all numbers per a population that is represented by a number not divisible by 10, toss them out). This is important because a lot of numbers will throw out incidents per country. The United States is the 3rd largest country by population, so any number by country will be higher in the United States as they can be about 5x to 40x higher than Western European countries.
I would also keep in mind that at a more individual level, the Democratic Party's position can run the gamut from "Repeal the Second Amendment" to actual political organizations like "Democrats for the Second Amendment". This isn't limited to the Democrats, as the NRA may be the largest Gun Rights lobby, but out of all Gun Rights legislation they only opposed two bills and partially opposed a third bill... their record on actual gun legislation is surprisingly okay with Gun Control... and they are criticized by some Gun Rights organizations for being too soft (notably the Gun Owners of America (in general) and Jews for the Preservation of Firearms Ownership (because Hitler was Pro-Gun Control for the Jews... when you're the JPFO, every bit of Gun Control is too close to Hitler's policies for comfort).
Basically, look at the lobbies and support of the general Democrats decision position (and even the Republicans... just because they generally oppose doesn't mean they all agree on what level of gun control is needed. Remember, the NRA has endorsed more gun control regulation than it has opposed.) It never hurts to read as much as you can on this or any issue. More information never hurts your opinion.