If he has a hankering for swords, at that age his first sword should be wooden. It is a time honored tradition for children and people learning to handle a sword to have a wooden sword for some time first.
Bokken, waster, etc.
Zieg
This....
Real Sword masters start with blunt wooden training swords first.
*(if you don't know how to handle a sword properly, you shouldn't handle a sword).
Second, never poor quality tools... Being frugal is one thing, you certainly dont "need" tbe best thing out there, but regarding any type of tool, wrenches, screwdrivers, (blades included), buying poor quality will lead to disappointment, replacements, or worse, injuries...
--Ie. You don't need a snap-on ratchet, but craftsman or husky are 100x better then some no name $ special...
3rd, daggers are actually illegal in many states still so check your local knife laws, but also they are designed more to be weapon of sorts as opposed to a regular knife. A 9 year old imho has no reason owning a (real) dagger: a rubber training dagger however is a pretty cool gift idea for him...
Fourthly; regarding the budK purchases, contact your bank and dispute those charges, with documentation of your initial purchase you should have no trouble getting refunded for those additional purchases, putting the fallout on them, and get yourself a new card.
Lastly, a pretty awesome (I think) "knife" for your nine year old would be a swiss army one handed trekker... Gets the locking main blade for a "regular" knife, plus the additional saw blade, screw drivers, and stuffs to do other misc. tasks with, like disassembling (and disemboweling) his other toys, lol.