You're welcome. My dad was a wonderful man, too. Makes it even harder!
As far as mentioning him at work, I did off and on and it made me shed a tear or two more than once! I had coworkers who were sympathetic and would hand me a tissue and a hug and others who would roll their eyes. So be it. People grieve differently. If your coworker cried once then got on with life, well bully for her/him. Obvs one can't spend a half day crying in the loo, but the occasional few minutes worth of tears shouldn't be criticized, especially at three months! I'm sorry if your coworkers aren't being kind to you. It's a poor reflection on them, not you.
The US is a huge country and acceptable 'grief' here runs the gamut from hair tearing wailing to quiet stoicism, depending a lot on where you live. Once the funeral or whatever formalities are over, expressions of grief such as tears or sadness where I live is, I think, pretty much accepted as long as someone isn't throwing themselves about and sobbing.
We still shed a tear over Dad from time to time. Most recently when DS1 was at the (baseball) World Series. Dad's (and our) team was playing and I told DS1 that if his gramps was still alive he'd be right there with him. Ds1 replied "Mum, he IS right here with me".
Those we love never really leave us.