Boltz Mini has a bunch of publicly announced channels and is decently well connected. You are the first to report an issue with it: https://amboss.space/node/03e9c5157126b8049ad235bdade8db97a473b5760b34781b8c870bd2ba34dbfcf8?section=Channels
It must be some limit you are applying locally to your routing that makes the payment fail. Anyhow let's continue debugging this in the support ticket you opened.
And regarding node selection: it's dynamic and we don't plan to expose this. The node we assign to a swap should always work for you and you shouldn't have to care which node. Let's figure out why you can't route to Boltz Mini.