I believe that the AICcmodavg package supports model averaging of occuMulti models with the modavg() function. I have not tried this myself.
If you have a positive beta value associated with an interaction term, that means that as that covariate increases in value, it is increasingly likely that the (two or more) species will occupy the same sites.
If it is negative, then as the corresponding covariate increases in value, it is less likely that the species will occupy the same sites.