Stress can trigger seizures also. I'm sure it has been stressful on him the last couple of days. My parent's first dog with seizures would often go months without one and then have 2 or 3 in a week, he was 18 when he died. The dog they have now has small seizures for a few days whenever they move back and forth between their winter and summer home. I'm betting that once he gets settled into your routine and gets some meds in him, it will be a rare occurance. After seeing a few seizures they began to pick up on some behavior signals before they would happen so they could move them to a quiet, safe place.
You are absolutely right about your dog easily ending up in a bad situation!! He is lucky to have found you. You won't ever regret adopting him. They give you constant, unconditional love and devotion. Our current dane had 4 homes in a year. The lady who had her before us treated her very well but due to unforseen family circumstances could not keep her. Prior to that we believe she had been kicked, had cigarette burns on her, and very malnurished. She was terrified of men as well. It was difficult for my husband the first couple of months. He loves danes and pretty much had to completely ignore her until she learned she could trust him. She now ADORES him. It takes her a few minutes to warm up to men but she has come along way in the 1 1/2 years we've had her. We stumbled onto her but I completely know what you mean when you say it was "meant to be". Keep us updated on his condition.