To add to Larry's comment, the reason they suggest baking the baking soda is to drive off excess CO2
, so you're not adding it to your tank... thus lowering the pH. As he mentioned, baking soda will act as a buffer, but not really raise the pH long term.
Sounds like the pH shift came from the ammonia spike - remember... excess biological activity will cause a drop in pH. And all that bacterial activity munching away on your ammonia is a lot of biological activity going on. If I was you, I'd just do 10-15% water changes every few days or so until your pH gets back to where it's at.
I dumped a bunch of baking soda in my tank when I first started because of "low" pH, so I feel your pain. Rebalancing the ca
relationship can be a pain after an episode like this, so here's an article to bookmark that might come in handy down the road.