I have to say - I think the OP has a bigger problem here than just a ruined Valentine's dinner.
1. Why didn't your DH tell him when he walked through the door (! that's a whole other thread in in itself!) that this wasn't a good night and show him out?
2. Why is it okay for your guests to walk in and help them to anything, let alone alcohol? I know some people like to be casual with their friends - but this was beyond the limit.
3. why did removing this guy become YOUR problem when it was your DH who caused the problem by letting him stay and not observing what he was drinking (which wouldn't have been a problem if he had been required to request a drink and your DH had served him and been aware of what his alcohol intake).
4. Why would your DH spend your evening sitting and yakking about Star Trek with his intoxicated buddy when he should have told his buddy to sleep it off on the couch and he should have been with you, comforting your child?
Sorry, but there are just so many issues going on here - a missed dinner is the least. Your husband was the one who was or should have been in control in every situation - after all, this is HIS friend - yet he allowed the focus of your evening to become his buddy, rather than you and your sick child. The friend was a jerk and needs to be aware of what a jerk he was, but your husband, in my estimation, let you down.