Clarification on Use Magic Device's first sentence on Spell Scrolls

Use Magic Device states that I use Intelligence as my spellcasting ability for a spell scroll, does that mean that I can use Intelligence for spell save DCs and spell attack rolls made with spell scrolls or do I still use the fixed spell save DCs and attack roll modifiers in the spell scroll table in the DMG?

I assume you mean the 2024 Thief ability. No. It's weirdly worded now.

When casting a spell from a Spell Scroll, you have to make an Arcana check if it is level 2+ spell. (Note that a 1 on this check does not automatically fail like an attack roll would.)

If the spell requires a saving throw or attack roll, you use the values on the Spell Scroll table; it is not affected by your own attributes. 

Certain spells will use your spellcasting modifier as part of the effect. For example, Cure Wounds heals 2d8 + your spellcasting modifier. A Thief casting that from a spell scroll would heal 2d8 + their Intelligence modifier. This is where the spellcasting modifier is used and they probably should have called that out for clarity.

This is a difference between 5e and 5.5e. If I'm not mistaken, under the 5e rules, following that example with Cure Wounds, a Thief would heal 2d8 + 0.

Still, an explicit explanation in the rules for a Spell Scroll would be nice, although it's true you can infer how it works by reading the spell's effect:

- Arcane Vigor (similar to Cure Wounds): "... Hit Points equal to the roll’s total plus your spellcasting ability modifier"

- Dispel Magic: "... make an ability check using your spellcasting ability (DC 10 plus that spell’s level)"