Sounds like you are doing everything per protocol. Are YOU the Alpha dog in the house? If not, that is your biggest issue.

The dog must submit to your authority and recognize you, your wife, any kids, etc.. at Alpha members. The pup is the lowest member in the family unit- period. Never tolerate aggressiveness or bad behavior. Nip that in the bud now or you are in for a world of hurt (including litigation). Sounds like you are on the right track with getting some outside help.

Good luck and hope it works out.