Hi Marcel,
1. Currently there is not a built in way to force a download. We'll see about adding that as a feature. However, in the meantime, you can create a Web Object and put your custom HTML in there. Depending on the location of the PDF (say if it's on a different server), this might get blocked. In my example (see image), I used the Asset Object to include the PDF file in the asset folder, but you could point to different URL, or place the PDF in the package post-publish - just make sure that you point to it correctly.
2. Hmm, it's probably worth taking another look at zapier as that will give you more flexibility. I don't have much experience with it, but generally speaking you can send data in SmartBuilder to a URL using something like this (see other image). If you have a sample of a zapier webhook working to send data outside of SmartBuilder, we might be able to take a look and see what's missing. xAPI would probably work to create a list of emails that would appear in an LRS (like SmartTracker), but you'd have to manually go in and extract them (probably).
Hope that helps!