Brahms Intermezzo in A major

This piece is a composite ternary form. Each section (A-B-A) can be broken up into their own A and B. I'm somewhat confused as to what to call the A section. Its hard for me to tell if the cadences are in the dominant which would make them IAC, but I could also hear them as half cadences in tonic. If they were in tonic this would make it a phrase group as every phrase ends on a half cadence. If it modulated to dominant it could make these two parallel periods. Bar 17 starts the b section of the A section. It serves as more of a developmental function which makes sense that in a composite ternary form, each section is Binary. The A section is open making the b section in dominant. The B section starts in bar 49 with a new melody of 8th notes. This phrase is repeated then goes onto the b section. The a section of this B section is closed, making the b section in the same key. The b section of the B section serves also as a developmental section. Bar 76 is when the A section comes back in. It is compressed as the b section starts sooner than before. For the most part the material is basically the same, just in different time durations. No brand new material is presented until the end with the terminative function kicks in.