If you mixed the salt in the DT then those are undisolved particules from you saltmix. You don't need to run your skimmer at this time because it is taking out the nitrogen source that is needed for your cycle. What did you use for a nitrogen source. Also you will need some LR
to seed the baserock that you have in the tank now. Don't worry to much about your PH at this time as it will be all over the place as your tank cycles. Raise your SG
up to ~1.025 as you cycle your tank.
Yes your skimmer should be in your first compartment so it has first crack, so to speak, at you undisolve food particules.
PS: Welcome to AA................