17 of Tammuz

I have been keeping the three weeks seriously every year. I also go to Israel around this time every year and it feels strange that the time of year that I should be joyous that I am "home" I am supposed to be "mourning", but I do it every year even when it feels un natural and counter intuitive. This past year I opened up an old Tanach I found that was my father's when he was a kid, there was a place holder and the page was in Yecheszkel. It mentioned Tammuz and scolding benei Yisrael at the time for mourning tammuz, a false god. Now that we are almost in Tammuz, I keep thinking about what I read. I am about to go to Israel again and I feel so strange now that I learned about this avoda zara of mourning tammuz. I learned that Sefardi customs differ with regard to the 3 weeks. Why do customs differ when it comes to Tammuz mourning practices? I am Ashkenazi, but can I follow the customs of Sefardi when it comes to mourning at this time? My husband doesn't care and thinks I should do what I feel is right. Is it an aveira to take upon ourselves a Sefardi custom?