Based on my experience, I would say your situation, as an employee, would warrant about 30%-35% if you have no out-of-pocket expenses and receive the benefits you mentioned. I don't know that your certification will get you any more percentage until you have few more years under your belt. If I were in your boss's position, I'd continue to be supervising you at the same level for a few years even after you receive your certificate. Depending on how you progress, as the amount of corrections and revisions decrease, then your percentage would increase based on merit and not time on the job. I would also continue to inspect the property as long as I sign the report.
Also, as an alternative to a flat percentage, when I started in commercial appraising, I worked on a sliding scale and received a higher percentage over a given level of production. for example, you might get 30%-35% of fees up to $100,000 and 40% for any fees in excess of $100,000. so if you produced $150,000, you would receive $50,000-$55,000. You could further get an additional 5% for work you generate from your own clients. This all gives you a production and marketing incentive and your boss should be able to afford the higher percentage as his costs per appraisal decrease with the higher volume.