Sorry for the trouble on your test. The fact that an email showed up with your download links means the order did process within our system, although it is very unusual that your free checkout page got stuck. We've tested the process and there's been no further problems like that and no one else has reported it, so hopefully that was a one-time glitch in the connection. If you ever have that problem again please let us know.
In a normal process a download link would appear in your browser, just as it did in your email. The process for a free checkout is also much different from a paid checkout, which would be handled at PayPal when actual money is involved.
As for discounts, it is not really possible to create true 3 for 2 or Buy One Get One discounts, although you can create price discounts that kick in when a minimum total is ordered.
For example, if your product is $12.00 and you want to offer a 3 for 2 sort of discount you can create a 33 percent (or $4.00 flat) product discount that only applies when three or more are ordered. That should come out to a $24 total when three items are ordered, but the discount would keep scaling up so that any further units added are at $8 instead of $12. Detailed instructions on using the various settings in our discount screen can be found here: