Tony didn't just go to the bar to have a few drinks with Alf. He went to clear his head, which is what he also said to Rachel. She seemed fine about him not going if he didn't want to, and then when he didn't, she copped a fit even after she was killed telling him it's OK if he passes. He gave reasons as to why he didn't turn up. I don't remember him saying "I didn't go because I didn't want to...". He's grieving, I think it's OK to pass on a few things when you just lost your son. She could have easily re-scheduled her ultrasound to another date for when Tony was up for it. She will most likely have another ultrasound in a few months time, so it's not like he missed out on some extremely rare opportunity.
Tony did a lot to make Rachel happy. He reversed his vasectomy so they could have a child. I think Tony needs to be cut some slack.
Rachel was also the person who turned to alcohol when her mother died. I don't see how her being pushed away by Tony for a few days is such a crime, as she did something much worse to Brad, Sally and Leah a few years ago.