We have pretty good data that shows how NRA members played an outsized role in delivering some important states in 16.
SCOTUS not flipping on the core issue of the Second Amendment being an individual right was worth what we spent and more. Had Hillary won, the Court would be at least 5-4 (and maybe 6-3) against individual gun ownership being a right. We also have 100 lower court judges and counting. Instead, we now have a Court that the other side is scared to take cases to. D.C. being shall-issue was the first direct result. There will be more.
I don't understand your repeated point about Trump creating new precedent for executive action. Multiple administrations have classified things as machine guns. The Bush 43 admin even classified a device and then reclassified it without going through any of the requirements of the Administrative Procedures Act. That reclassification was upheld by the 11th Circuit. We don't agree with the administration's position on bump stocks (I even wrote these comments that make that very clear https://www.regulations.gov/document...018-0002-87401). You also seem to have a fundamental misunderstanding about whether or not a particular executive action is legal having an effect on some other type of administrative action. One type of executive action doesn't justify another. Obama also tried to take executive action on various gun sale loopholes, but his admin discovered that FOPA closely constrains available administrative action when it comes to defining who is "engaged in the business" of being a firearms dealer. Three years of effort led to the creation of this booklet: https://www.atf.gov/file/100871/download, which is about all that they can do on limiting gun sales without Congressional action.
I know you already expressed that the ATT being unsigned was not a big deal, I disagree. But, I think this is also the beginning of the administration looking for positive things it can do for gun owners, not the end.
No one in Congress fled from positive gun legislation, we simply didn't have the votes in the Senate to get to 60.