Ask for the higher equity possible. Sit down with the CEO and other cofounders if any. Talk to them about what they have in mind... don't tell yours yet... listen. With your experience, with your 4 months without receiving salary, watch out, be smart. Marketing if done right is a hard needed task in businesses. Be creative, that is part of what you do. But don't be intimidated. Come up with ideas for them to ponder if they are unsure of how to keep you. I would count how much of the equity is giving to whom in exchange of what, and position myself (for the remaining equity if possible in some situations). I've been in a couple of proejcts in where equities were study over certain months and open to renegotiate. I started in one business with 49% of it. We all decreased when we brought one more person. And finally my plan have an exit strategy in place. My intention was doing what I love doing, helping someone bring their idea up, delegate and train, and move forward. We are friends, and once in a while we (the ex cofounders) consult on each other expertise.

Success to you!