pricelessbrewing
Brewer's Friend Software Manager
I think the general rule of thumb is 15 minutes before the end of the boil to sterilize it. I looked for some recipes, and the ones I saw either did that, or at the start of the boil, so I think you'd be okay either way.
Sugar addition timings don't really matter that much, apart from a slight change of utilization for hop additions.
Also boiling doesn't sterilize, it sanitizes.