The swarm gorged themselves on honey before leaving the mother hive. It is enough to last them 2 or 3 days, so with that and a hive top feeder, I would expect foraging to be slow, especially in bad weather.
Leave them alone for a WEEK, not a month. Give them time to lay eggs and have larva. Then it will be safe to open them.
Now, get a hive ready and make your split. It sounds like you have that under control.
Also get another hive ready, as another swarm call will be coming in shortly.