Screenwriting : Moving on to the next step of the screenwriting process by Krista Crawford

I'd been working with a company to convert a horror comedy feature that I originally wrote as a 60 minute pilot to a feature and after a couple drafts of a synopsis, they have sent me an option contract back in January. They get first rights to be decided within 4 months of the final draft (I was given 3 drafts).

After each draft, we would meet via zoom and discuss the script, what they liked/disliked and suggestions for the next draft. After the 2nd draft, they told me that they really liked the script and they were planning on going forward with the project even before they got my 3rd and final draft, which was sent to them last night. They asked me to start thinking up my dream casting choices as while they were committed to seeing this through themselves, they had enough confidence in the script to start reaching out to some of their contacts to try and get some bigger casting names. They also said to start thinking about what I wanted out of this, going forward and that they next time we talk, they will start crafting a new agreement with me.

Now, I am under no illusions that my script is going to get made or that I'm going make bank or anything, given this is my first project to get to this stage. But I would also love to be a part of the process if it does go forward, which is something that has been hinted to me by the execs I've been talking to (this is a very low budget company and script). My question is, I'm not sure what I should be asking for. 2-3% of the production budget is what I've read/heard that I can ask for for the script purchase price. The company also mentioned a producer credit if I want, which could offset some of the outright script price. How do I mention that if they are going to actually make this themselves, that I would love to be involved and possibly get paid that way? Is that an option I can ask for or do I just take whatever price I can negotiate for the script and royalties should it get distributed?

Any suggestions or help or feedback as to what I should be discussing would be great. I do have a pretty good relationship with the two execs I've been dealing with and we respect each other and they have mentioned a continued working relationship with me even after this but they are a very low budget company so I'm definitely not going to be getting 6 figures for the script or anything so I want to go into this being realistic. Thanks all!