I often alternate the drenches, you may want to get a 30 cc feeding/drenching syringe in the feed store. you can use all of them,
I sometimes alternate,
another drench I make is plane or flavored yogurt mixed with one egg and thin with a little water or 50% dextrose and drench with that.
I was really giving you options to see what you have on your shelves in your kitchen.
to me the bakign soda and Penn G are the priorities since you have already been getting liquid into him, the other things are to alternate and just give him energy and fluid, since he is getting so much milk he is getting protein and fluid, that is good. Really can do all of htem or try one of them, was just giving you options.