Join Date: Nov 2013
Location: Cape Cod, Massachusetts
Well, I don't know about the hissing, but it definitely isn't safe to leave him loose in the house when you aren't there with all those big dogs around, especially since some are less than enthusiastic about him from what I gathered.
How long have you had him? Are you doing intensive socialization with him, i.e. handfeeding (baby food, etc), lots of cuddling and massaging, etc? It would be best to win him over before he gets too old if any way possible for optimum results.