The company you are applying to makes a HUGE difference in the salary. The range can be huge. So it is very difficult to answer that part of the qn if 3.9 is ok or not. You probably need to give some background of the company(ies) you are applying to so we can help you here.

As to how to increase earning power, erm... make yourself employable in an area that is more urgently in need of talents? Your qn is very wide... I mean you need to sit down and think through what you really want.

What is your interests? What is your career plan? You want to increase earning power through what and where? Is it still by doing accounting? If so, for long term accounting, please go get a CA. If not necessary in accounting, which area you want to venture into? Do you have the skills in that area? If no, are you willing and prepare to acquire skills in that area? Otherwise, are you able to enter as junior roles in that area? You know auditing/accounting industry is evolving also, right? May be try to make yourself employable in the new area it will evolve to?