If you look at the packet of levamisole drench powder, you'll find different mixing directions. You can mix the standard drench (for cattle) by adding the contents of the packet to one quart (32 oz) of water. To mix the concentrated drench (for sheep), you mix the powder with 17.5 ounces of water. The different dilutions for levamisole are just a matter of different volumes to administer the same dose of drugs.
The safety margin for levamisole in sheep is about 3X. In goats, because we (ACSRPC) recommend a 1.5X dosage, the safety margin is less than 2X. So -- there is a reasonable safety margin, if the drug is dosed appropriately. A 20 to 30 percent overdose shouldn't cause a problem.
Only the avermectin drugs affect dung beetles. This is because the avermectin drugs have potent insecticidal activity AND are excreted mostly unchanged in the feces. Levamisole has no insecticidal activity. Ivermectin is also much more persistent than levamisole. The half life of ivermectin (in sheep) is about 4-5 days, whereas levamisole has a half life of a few hours. That is why repeated (next day) dosing of levamisole is safe.