Hey there!
I also use Weebly for some sites, and "Eliminate render-blocking JavaScript and CSS in above-the-fold content" pops up quite a bit as an error.
I've played around pretty much all day to try to figure out how to delay the JavaScript and CSS, but to no prevail. It looks like Weebly's take on it, is since they're a live site, you can't make these changes.
It seems this is the case, but wanted to reach out in case there could actually be a solution, as I've tried pretty much every one I've found online thus far.
Thanks for the help :).
Patrick