EB2 or EB3 on my position

剛收到一個OFFER, 工資不錯, 比LEVEL 4 的工資還要高15%. 但老板隻能辦EB-3. 因為不知道我走了怎麽辦. 他堅持EB-3. 但我說job deion is depends on the person. you can change the deion if you hire next person or set up position to fit my skill set. I just wonder can he set up two positions with similar job deions and one requires master or 5 year experience, the other with less experience and a bachelor and apply me to the first one. the difference is the salary. Anyway to pursaude my boss on this? Also can he change the job deion later on when I leave the company? that is his main concern. I think it always should be ok since the enviroment is changing always....

Second think, I have an MBA, CFA and CICPA. can I apply NIW and eb2 by myself while they do their filing?

Thanks in advance!!