1) The 2A is not a hobby
2) Homicide rates have been dropping for the past 20 years while there are more firearms purchases than at nearly any time in history. It is counterintuitive and contrary to the facts presented by the government criminal justice and health agencies for Antis to claim that we have a public health risk that requires anything exceptional to be done.
3) High homicide rates in specific urban centers like Chicago, Baltimore, Detroit are cluster problems and not national problems. Remove those clusters and the statistics for homicides in the United States plumet.
4) Regional data from the FBI Uniform Crime Report shows NE states like Maine and New Hampshire have lower homicide
rates than states like Massachusetts even though they're in the same region and Maine and New Hampshire have liberal gun laws with few restrictions and Mass has restrictive laws for gun owners.
5) Semiautomatic firearms have been common since 1906. The homicide rate peaked in the U.S. in the mid '70s and the early '80s. Homicide rates are down since.
6) Semiauto rifles are a statistically insignificant factor in homicides. Any restriction is not based on risk based decisions.
7) The mass murders you've cited (and those you haven't) make no statistical difference in the homicide rate. The murders are dramatic and tragic and captivating to the news, but they are actually rare. The government studies have identified them as rare events that don't influence the rate of homicides. Why use rare events that don't represent a public health risk for the basis of a broad confiscation scheme imposed on the millions of gun owners?
8) The number and therefore the rate of mass murders has gone up recently, but there's no trend. They're still very rare. The fact that the number of very rare events goes up doesn't stop them from still being very rare even if the rate of those rare incidents is doubled. Statistically, they still don't constitute a risk to the population. Fear of them is like fear of sharks because of reporting on shark attacks even though those are very rare events (more people died due to "selfie" accidents than shark attacks).
9) The United Nations Office on Drug and Crime provides homicide rates for reporting countries. The latest report shows that the US has a greater DROP in homicide rates than Canada and many European countries. While we have a higher overall homicide rate we are dropping faster than countries often pointed to by Antis as "better" than us. This, again, in the face of a clear increase in sales of semiautomatic firearms.
10) There are an estimated 300 million firearms in the U.S. 1/3 of the households have those firearms, i.e. over 100 million. The CDC recently reported that firearms are used defensively anywhere from 500,000 to 3,000,000 times a year to protect people. You are 50 to 150 times more likely for a firearms to be used defensively than in a suicide and 100 to 300 times as likely for it to defend a life than be used in a murder. There FBI and CDC data do no support the common anti myths.
11) Highly politicized and emotionalized issues often lead to emotional and political discussions that aren't fact based because of the emotionally targeted propaganda. It is the obligation of anyone that wants a rational discussion in that arena to get the facts and to try to understand them before presenting draconian controls for a problem that may not be significant enough in reality to impose them on the general population. Emotions may motivate, but they aren't a good basis for decision making.
12) The CDC has pointed out that "gun control" measures have not shown a clear benefit. Nothing that is proposed in the original post is workable considering it constitutes confiscation of private property in the face of the Constitutionally guaranteed right. Individuals do not comply with these approaches in the states that have implemented them, States would not comply with a Federal effort to do so, workable percentages of law enforcement and military personnel would not willingly enforce such a prohibition and confiscation. Any proposals that are unworkable are emotional pandering instead of practical risk based mitigation to a recognized threat.
Perhaps a review of these threads that touch on your fears would be helpful settling your mind.
http://www.thehighroad.org/showthread.php?t=789590
http://www.thehighroad.org/showthread.php?t=789654