Resting heart ejection factor has stablized at 35-40%, improves at 45-50% under stress. how to improve resting ejection factor?

Depends: Depends on cause, duration and whether you're a candidate for resynchronization pacing. The standard therapy to improve ef is a combination of betablockade (especially carvedilol/coreg) plus an ace-inhibitor taken daily for months to years. Some forms of cardiomyopathy are not reversible, unfortuntately. Since you've had a stent, a careful look for hibernating myocardium is indicated.