They both act on GABA, although Etizolam on GABA-A and Baclofen on GABA-B so at a guess there may be some potentiation but I wouldn't be able to say for sure if they are safe together or not. As far as I'm aware Baclofen is sometimes used for people who suffer spasticity and also to help with symptoms of Alcohol withdrawal (As are Benzos sometimes)
I'd just say take the Etizolam and then smoke some weed
It depends what you're looking for. For recreational purposes, neither benzodiazepines nor baclofen are known to cause great euphoria. Some may disagree.
In any case, don't mix sedatives, as it may cause respiratory depression, and possibly death.