Animal Care Needed

I have 2 Dachshunds one is very mellow and sweet. I adopted a second from ACS a year ago and he loves me yo death but can batk at strangers and has bitten my teenage son on his thumb when ny son tried to pick him up [fear bite] he is submissive and will go to his back which tells me at some point he may have been beat prior yo me owning him. I need someone with experience with a Dachshund like this for times I travel. My biggest fear is he bites someone again. He is a lovable dog but has trust issues, so I don't trust him around small children etc..... or strangers that reach out and try to pet him out of nowhere startling him etc.