If you've received starting offers 30k-50k more than you are currently being paid in a comparable/better company, you have two options:

1. Tell your boss you're getting an offer for 30k more. Ask for that amount or a considerably larger profit share. 30k in direct compensation is worth 60k in uncertain profit share (3.5%). If the profit share were high probability, he would offer you direct compensation instead because he would prefer a superior outcome for himself (higher profit).

2. Leave and work for the other company. 30k is a lot of money.