I think if you are a smaller operation and you have specific requirements that you've thought out and aren't covered well by basic tools, then getting comfortable with JS and SQL (or R or matplotlib or Jupyter or whatever) is going to be the best way.
I've spent too much time watching people spend months and tens of thousands trying to bend 12 different third party tools together when a developer could do the whole thing in a week and it would actually do what you want it to do.
Nailing down the actual requirements is the hard part of building your own dashboard, it sounds like you've done that. If your needs are stable-ish or you have consistent developer resources it's going to be hard to find a better fit than that.
This. Freelancing is the future. Hiring in-house developers, or better still, freelance programmers will ensure that you will have custom-built your maximum BI tools and with a reasonable price. Of course, finding and hiring good freelancers who are not only dedicated in their craft, but also reasonably priced is a bit involved task, but certainly doable.
That's why I was repeating the importance of him having some well thought out requirements. In situations where this is true (and it really happens sometimes), I've regularly seen good developers come in under budget and mediocre ones at least come close.
In 99% cases, that happens because your requirements change. If you hire a competent developer, the total cost of development is always a pittance compared to what you pay monthly/quarterly to a product based company.
I've spent too much time watching people spend months and tens of thousands trying to bend 12 different third party tools together when a developer could do the whole thing in a week and it would actually do what you want it to do.
Nailing down the actual requirements is the hard part of building your own dashboard, it sounds like you've done that. If your needs are stable-ish or you have consistent developer resources it's going to be hard to find a better fit than that.