I'm Canadian so I'm not a voter in the contest you're presenting, but if I were I would vote Democrat. And of the trio you present for the Democrats, I would say that the position I'd compromise on would be gun control. Not because American gun culture isn't bananas and it's not a serious problem, but because I can't see any plausible way to fix it in the short term. So might as well let it go for now and deal with the more important stuff that affects more people.
I think a more reasonable compromise would be to give Republicans most of what they want on immigration reform. That seems to be something they consider to be of critical importance, but that I think can be allowed without it causing significant harm. If the American economy starts to suffer as a result of not having illegal immigrant workers then that will be motivation for further reforms. I think it's important to have the laws try to reflect the realities, though, and having the economy literally depend on large-scale lack of adherence to the law of the land is a bad place to be. Just make sure not to be monstrous about it - don't do the concentration-camps-for-children thing, try to maintain basic asylum access for those who truly need it, and so forth.