BTW, it is worth noting that the FDA is considering limiting the amount of peroxide citizens can buy.
It's easy enough to make that serious terrorists wouldn't be hindered by that move. It's not a bad idea to limit the concentrations available to random consumers (already done), and limiting the total amounts could provide some safety benefit in terms of stupid teenagers trying to make homemade explosives, etc, but I don't see the possibility of enough benefit to justify the infringement on freedom of a blanket restriction on quantity purchases from a bricks-and-mortar retail store. I'm sure there are already limitations on shipment of large qunatities of highly concentrated hydrogen peroxide (if only due to shippers' safety restrictions).
The stuff isn't terribly hard to concentrate to 35% or so. The most restriction on in-person retail sales that would be reasonable is along the lines of requiring ID to prove you're an adult before buying more than a couple of bottles at a time. Make it difficult for stupid kids to buy up a bunch and do something dangerously stupid with it.
Frankly, there are other things that should be higher on the priority list for sales restrictions to minors, from a safety standpoint. Acetaminophen (Tylenol) tops the list, since it the leading cause of acute liver failure requiring transplant (in the US), and the effects are greatly increased by alcohol consumption. Yet nothing at all stops a 14 year old girl from buying a bottle of Tylenol and taking several to deal with her hangover, and then swallowing even more without realizing it when she pops a Midol she bought for her menstrual cramps and bloating.
It makes sense to have some restrictions on bulk purchases of the sort that you wouldn't find in a retail store, similar to the current restrictions on bulk ammonium nitrate fertilizer purchases -- but that wouldn't have anything to do with the FDA -- more like the BATF and/or DHS.