To setup ECS with a domain + SSL, you need ALB. I've researched and couldn't find alternatives that weren't wild. This sucks, because ALB is expensive. If this ECS service is your bread-and-butter service, then you'll want ALB eventually anyway, great. If not, suck it up buttercup.
The order of steps you take to set this up are important, you can't easily mix/match these steps, which is why I'm creating this post. I've found other tutorials, but they didn't peg the order exactly and I hit snags.