The way I do it is copy-paste the easing values in the text box, drag-and-select all the keyframes I want, and paste the easing values in the text box to apply it to all those keyframes.
Regarding an easy way to choose an easing curve, I’d also like to see a chart to choose from, but until then I suggest keeping https://easings.net open (not affiliated). They don’t do custom curves, but they have all the standard curves (and their inverses) you can copy and paste into your animation. https://easings.co does have custom curve support.
I agree there should be an easy way to reverse a curve. Until then, use this easy formula: If you have a curve
x1, y1, x2, y2, the reverse of that curve is
(1 - x2), (1 - y2), (1 - x1), (1 - y1).