Feeling undervalued. I will not promote

I just had a meeting with the other 3 people in my company. I'm the only tech guy. I built the entire product and all the infrastructure to build, deploy and run it. The value of the work I've put in over 2 months has been externally valued at 350-550k and should have taken a year(!). They've paid me perhaps 1% of the value added. I tried to have a grown-up conversation with them today about equity reflecting value and got basically stonewalled on that and also a flat refusal to increase my rate to something I might be able to survive on. I'm feeling so undervalued right now :(