3 years is too low. IMO you should align your thinking with the 4 year halving cycle + the occasional year or two because I doubt this is that exact. Always leave wiggle room in your expectations.

DCA VS lump sum makes no difference. I have done both. Do what you can afford to do. I suggest DCA for most because it allows you to put 50 dollars into an account every month and have it just auto DCA. All you have to do is make sure the cash balance stays good. This keeps your finances flush with cash as opposed to if you lump sum and then need that cash for something unaccounted for a week or two later. Don't stress your finances when you don't need to.

I don't know anything about the math and stuff. That is going way too deep.