i see you didn't get to many answers. getting one from MB is like getting a bunch from the rest of of anyway :-)
if you go by the discussions here, most of us have given up the antibiotic treatments, etc. there is the cost. also, for me, prophylactic antibiotic treatment does not make sense to me. if they bring the stuff into the hive, you can't cure it, you can only keep treating for it forever..
your mite count was high. the apiguard gel trays work well. you can put them on the top box, but you need a spacer to keep the lid off the tray. i make mine with some 1x1 pieces of wood. anything will do as long as it is pretty much air tight. you need temps + 60 during the day at least, and each hive will take two trays put in about 10 - 14 days apart.
be happy your hives are so heavy. many of us are spending lots of money on feeding this year!