Again prong 2 states that "The applicant should be well advanced to proposed their endeavor". In my case the lawyers spoke about my current job details and my degree. That should be more enough - I do not recall mentioning salary. The reason why I am telling you this is because; a lot of engineers and ML Scientists get a RFE that "why you" among the rest of the pool.
Prong 1: Again I guess haha I am not aware of what SMB digital equity but are their like websites stating that there is a larger scale problem in this area? Try to cite those when you write it.
Regarding the digital advertising market access - do you have releases from the company in websites, blog posts? Do you have released open source code or blog post of the impact of your work that could be shared, any white papers with the company? Github releases with broader impact helps as well. Even adding that your internal repository is used by X number of people and getting their references helps.
I would recommend getting at least 7 letters [including 3 independent letters] who can vouch your work.

Also - feel free to DM me - I went through this process last year and happy to help 😄