She sounds very similar to my JRT Rosie, she is a very itchy little dog!
She had all the -*test*-('")s, skin scrapes, biopsies, allergy -*test*-('")ing etc which cost a fortune

which all came back pretty much clear.
I bath her every week in medicated shampoo (the Vetplus one) which helps alot.
She always seems worse too after country/wood walks as oppsosed to the beach.
Hope the antibiotics and flea stuff helps, it might be worth thinking about shampooing occasionally, it's certainly helped with Rosie, and kept her off the dreaded steroids so far
XXX