Kristen, I'm sorry.
We all have set-backs. Hopefully you've had a little sleep and are feeling a bit better.
Years ago, Simon bit a woman and it was one of the worst days of my life. That's when I went to positive reinforcement and started learning about fearful dogs and dog behavior. I felt way, WAY in over my head. My boyfriend and I were about to bring Simon to live with us and his daughter, so the timing could not have been worse.
Simon was fairly old by that point, but he still had a lot of years left in him and we did a lot of management.
If I were in your shoes, I'd have Toby checked at the vet's, if you haven't already (I couldn't remember...)-- checked for pain, thyroid, eye/ear problems, etc. Anything that may be causing physical discomfort or pain or instability.
Then I'd go into management mode. I know we all want our dogs to be as social as we are; we want a dog we take to the store and to people's houses and the park, but I wonder if some dogs just aren't cut out for that life. With Simon, he got walks around the neighborhood and car rides, and lots of time with us at home, but I never took him to the store, always went to the vet's the minute they open (it's a walk-in) to avoid the crowd, and didn't really have people over. We had a couple of friends who came, but they knew the drill-- Simon generally went in the yard or another room while they came in; they had treats they could drop on the ground for him immediately or wait until we'd settled on the couch, and then they basically were instructed to ignore him completely, which was hard; he'd put his head in their lap and practically crawl all over them as long as they ignored him. Only people I could trust could come over. And there were certain things that Adam couldn't do with Simon. They lived together for years, but with certain things, only I could handle him.
It all just became part of the routine, part of our lives.
With Robin, we have to do a little of the same management, and it's even harder for people, because she cannot tolerate eye contact from people she doesn't know. And if she hasn't seen someone for a couple of weeks, she's a little wary of them again. If it's not someone she lives with or sees very, very regularly, she's extremely skeptical of them. And if it's dark, if she can't see us very well or immediately, she'll bark at me or Adam until she can see us well. If Toby was already going over threshold, and Allen approached in the dark, maybe he freaked and then just had a hard time cooling off. Was Allen then staring at him while he was freaking out? Talking to him?
Like I said, if it were me, I'd have him checked out, and then go into management or at the very least, require less sociability from him and ask the people around you and him to be aware of their bodies and facial expressions. And then I'd schedule another visit with Kathy Cascade to talk about some of these things.
Hang in there.
I think there might be a lot of details worth dissecting in what happened. You might start building a pattern. Even though he knows Allen, he may not see him as his owner/handler since he's probably not the one who feeds him, walks him, etc., and so the same issues may apply.
Keep your chin up.
"In these bodies, we will live; in these bodies we will die.
Where you invest your love, you invest your life." --Marcus Mumford