Most home-made emulsions have a lot of dead grains and you are coating more silver than you need. In this case, the emulsion is not sensitized with sulfur or gold so this gives even lower speed. You need a higher activity and more concentration to give better contrast, but your image above looks better than the description in the OP, it just needed a long exposure.

IDK what Mark used, I forget, and he is on a trip right now IIRC. I am supposed to have lunch with him in 1 or 2 weeks so I'll ask him for suggestions.

Myself, I use DBI under dim red safelight and D76 with no dilution. I use 10 minutes or more. Typically, if you watch the front and back, you can see the front develop much more rapidly than the back.