I don't think it's anything to do with being too alkaline. The human body has PH regulators that maintain the level, and it's acidity that is the problem anyway.
That does sound like an awful amount of things to do through in a short period of time.

I can relate to loss of strength, or at least muscle. I used to always be rather muscly for no apparent reason, as I didn't work out. But, after becoming vegetarian, I lost quite a lot of muscle. I have never been very self conscious of my body in any regards, so it was not enough of a reason to make me start eating meat again, and I don't feel physically weak.

The other issues sound a lot more serious and I haven't heard of this happening to someone who quit meat before. Because it was only over a period of thirty days though, how can you be certain it was in fact that diet and not something else?

I don't wan to recommend trying it again in case it was in fact the diet, but might be worth thinking about what other changes you made in your life at that time, because it may not have been the lack of meat.

Based on the symptoms it does sound like some type of nutrient deficiency if anything, but perhaps something a lot more prudent than B12, like protein. especially in regards to the weakness. If you go off meat you need to ensure you are eating foods with plenty of protein in them. Nuts are really the best for that..