I'm afraid the same is true of using offal as BSF food and then feeding the larvae to the same species that produced the offal. I don't know a lot about this subject, but the people who produce the BioPods clearly state that this type of loop is risky and not recommended.
Since you have fish to feed you can always use the larvae produced from chicken scraps to them. Also, I'll bet the BSF larvae will do fine on the alpaca manure so the chickens don't need to be left out.
I don't think you'll have a problem draining the liquid into the ground. It's best if the liquid isn't exposed though, because a significant number of BSF females might be attracted to it and lay their eggs outside of your units. If the units are sitting directly on the ground it shouldn't be a problem.
