I entered the corral alone today!
I did the feeding and helped with the mucking as we have been doing for the last few weeks. Since this has been working well, I asked my husband to wait outside the gate while I put wood pellets on the muddy spots of the big boy corral.
I carried my trusty tennis raquet, told the alpaca to move back and sprinkled wood pellets on the mud. For the the most part he respected my presence. He did not enter my space, but took longer to disengage.
When we finished and I exited the corral, I was shaking like crazy. But I was in the corral alone! I consider this major progress. We will do this a few more times before moving to the next step.
I want to thank everyone for the positive feedback and support. I am encouraged to learn that some have had similar situations with quick and positive corrections.