1. From the map of this paper (attached, Fig.3) and this map from TAIR website( https://www.arabidopsis.org/servlets/TairObject?type=vector&id=1001200279 ), you can design a primer from Nos terminator region (Tnos) just outside the TA- cloning region to sequence your inserted DNA. It looks like that the Nos terminator is unique on the pCXSN-myc vector.
2. The TAIR map did not indicate the -TA- cloning location.