His behaviour re: drinking and promiscuity does suggest that he is trying to escape the grief and pain that would be haunting him. It is also possible that his peers in this setting don't try and discuss any topics of emotional depth, rather just 'have a good time'. The main hazard I would nominate would be him using alcohol (which is a depressant) to self medicate his depression and trauma.
The positives (yes there are positives in this!!) is that by going out and interracting with others, he is increasing his protective factors by managing his social isolation. Also, as much as the promiscuity would be at odds with your family's religious beliefs, it is a means of him releasing endorphins, activating seratonin and dopamine which all relates to him being able to 'feel good'.
Has Zoloft been working for him? Is he regularly taking the correct dosage? (Not for you to answer but more as something to discuss with his practitioners).
If he is getting up, going out, being around people and able to give his mind 'time out' from the trauma, then that is a good thing. When he isolates himself and is socially withdrawn is the time to get very worried.
Hope it all works out for you, no doubt it is a long road ahead for all of you with him.