You are severely limiting your journey options by splitting your tickets at both Freshford and Theale.
Another option would be Bath Spa - Cholsey CDR (£11.90 railcard) which has an easement permitting travel via Reading, where you can stop 'short'. Then a Reading - Hanwell CDR (£9.05 railcard) which also has an easement, permitting travel via Paddington, where you can again stop 'short'.
Travel is then wholly via the quicker GWML.
Best with this combination to actually alight at Reading in each direction (plenty of HSTs call - on the return I use a South Wales bound service off Paddington, then change onto the following Bristol Temple Meads service 15 minutes behind) and remember the evening peak restrictions from Paddington if travelling on a weekday.
Some might say that you can't stop short when using an easement, but there's nothing in the ticket restrictions or Conditions of Carriage that forbids it. You've been given an additional right to the route you can take. That hasn't removed the rights to start, end, or break and resume your journey at an intermediate station provided your ticket type allows (which is so in the case of the CDRs I've mentioned). Reading has become an intermediate station on your routes thanks to the easements.