"currently, 100% of the design AND code was created by me."
You may have done the typing, but you also acknowledge that there was a lot of discussion that led to the current design. I guess that this is an area where your co-founder may see things very differently ('(s)he did the technical stuff, but all the ideas are mine')
As to your question, you should decide what you value more: getting back on your co-founder, or having the product succeed. In the first case, go talk to a lawyer; in the second, I think you should get an agreement that includes you leaving the company ASAP. That ASAP is because of phrases such as 'bullied', 'bosses me around', 'belittling' that make me wonder about the 'is' in 'who is a close friend.'
How much you can get out of it depends on the value you have to the company. That will depend on the technical complexity of the product.