This is a very good suggestion and this is what I will don since I've always done IF. But, to try whether it is better to stop working out or continue with some modification to the diet and workout, I will put myself on an experiment. I'll fast early 
How much gain? A lot, if you didn't control your diet. You have to adjust your calorie maintenance and eat accordingly. If not, your strength will diminished, your muscle will becomes smaller as what just happened to me