TXSP10 fare is Mon-Thurs with last outbound 3/13. Sunday return is your problem. TWSP10 fare is Sat-Sun with same outbound restriction but you wouldn't be flying outbound on a Sat-Sun so fares can't be mixed on a half-round basis since TWSP10 will not apply after 3/13.

There are other fares but I picked cheapest (560 and 610+, respectively). Rules and availability may be/will be different. S and T fares appear to have similar specificiations after cursory glance.

I believe this info can be found using free KVS tool.

Pat