While the text of the feat is somewhat ambiguous, there are several indications in the rules that touch spells are not valid targets of Persistent Spell:
- If spells with "a fixed range" were intended to include touch spells, why are spells with Personal range called out as allowed? After all, "Range: Personal" is no more variable than "Range: Touch."
- The errata for the book in which Persistent Spell was originally printed, Player's Guide to Faerun, explicitly said that touch spells could not be persisted. While subsequent re-publishings of the spell did not include these changes, they're indicative of what the intent of the feat's wording was.
- Heroes of Battle p. 113 describes the effect of War Weaver's Enlarge Tapestry class feature:
you cast through an eldritch tapestry have their range category increased: touch spells become close range, close-range spells become medium range, and medium-range spells become long range. Long-range spells and spells with fixed ranges are unaffected.
This rule explicitly draws a distinction between touch spells and spells with fixed ranges, and treats them differently, implying that touch spells are not included in the category of spells with fixed ranges.