This will not cure the "problem", but it may prevent damage. Stop drinking/eating anything with caffeine, and limit exercise to lower aerobic range, say with you HR under 160 (assuming your are in good condition, just can't take extensive physical stress). Take a good look at your overall diet and try to eat as healthy as possible - how is your weight and anxiety/depression/general mental health? You don't need to answer, I am asking more for you to think about it as it relates to you heart concerns.
As for an EF of 49%, that is on the low side, but should serve you well. It may be well to have that checked every "few" years to be sure it is holding. Because of my heart condition and advanced years (compared to you) I get an echocardiogram at least every 5 years - this is one way to measure EF, there may be others.
at least perhaps go to see a reg gp and ask for a 24 hour monitor of you can