Wow, you sacrificed a lot for the woman you love. Sounds like she is really lucky to have you!

We all know that its just another religion, although that realisation may take years to get to even though you have your doubts. Its just a case of putting forwards an argument that in the right setting and mindset cannot be refuted. Read the book Gentile times reconsidered (4th edition), can find easily on google as a e book. As soon as they know it's by "apostates" they wont even listen to you, so study it and try and put it forwards as your own logical thinking, that you saw in some history books. The book quotes all its sources so you don't have to show them the book you got them from(unlike the unreferenced watchtowers). The book even has a section on countering the most well thought out responses.

My family keep saying "but you know its the truth" and every time I bring up a point or two from that book, they go quiet and seem to pretend that the conversation never happened

I'm sure I will get through to them one day, just one smiling patient lovely step at a time. Its hard to not fly into a rage when they come up with the indoctrinated responses, but you need to keep calm.

As soon as the eschatology is wrong, or even doubted the whole façade falls down. At least in my experience!

Good luck!