I can't find that Epic Level Handbook feat. Are you sure it is from there?
I like the idea of it but am not sure about why you get to add a full ability modifier to what already has an ability modifier for each scroll in the first place. Maybe they wouldn't stack.
Ramble on....
In any case looking at that chart, magical item save DC's stink.
You can't improve them and characters and opponents are most likely going to save from effects being used against them just because the magical items/scrolls that enemies use are around the same levels and abilities of your opponents.
In other words, you and your opponents should never have items beyond their level, and since these items/scrolls have low DC's you or your opponent is most likely going to save when the item/scroll is used.
Characters over 6th and 7th level start making most all of their saves when confronted with magical items of appropriate power. How many CR 6 and 7 creatures are walking around with 9th level magical items? None! They have stuff based around 3rd and 4th level spells, tops! Your PC's are more than likely going to save!
Rambling off....
Aluvial