Most welcome - happy to see another Canuck hereabouts My mom's just down the road from you in Arnprior.
If you were able to get the initial broken links review corrected within two weeks, that's great - not much of the authority should have dissipated.
However to note - the 404s in Search Console aren't the only ones that need to be fixed - they're just the ones Google has noticed and alerted you to so far. The problem with relying on GSC to tell you what to fix is that, by the time it has shown up in the Console, Google has already hit a 404 and been told it's a missing page. It's totally reactive, instead of proactive.
I'd strongly recommend you also use the other methods I mentioned to get more of the old URLs found & redirected as well before Google notices they're borked. It's also ideal if you can try to get the owners of the most valuable sites that linked to you in the past to update their links to point directly to the new pages. It's a bit of a battle, but even just a few updated can make a difference.
As far as how long until "link juice starts flowing" by which I assume you mean "rankings and traffic start to return" - the only real answer is "it depends", I'm afraid. You'll want to submit your new sitemap to GSC so that you can track the progress of the indexing of your new site's pages (on Squarespace, the URL to submit is www.kanataskinclinic.ca/sitemap.xml). You should also do this for Bing's Webmaster Tools.
Since URLs and content have changed, it's going to take some time for your site to fully re-index and for Google to understand the value of the new content. Could be from a few weeks to a month. It would also help to submit a few of the main section pages using the Fetch as Google tool in GSC and to get some new, strong incoming links to the site's pages. Good social links, and at least one or two new ones from relevant sites.
Lemme know if you have further ??s
Paul