The trigger/magnet fits over the crank, on the side of the motor nearest the seat, and sits inside the “donut” of the stator. The magnet position is fixed by a key in the keyway on the crank output shaft.
If the “original magnet” you speak of was off a push-button start ignition system, it won’t work correctly with the key start system and this explains your weak spark. Though, to be honest the motor will run with the wrong magnet (I’ve done it–blush) so this does not totally explain the non-start. My guess is the the weak spark combined with no choke may be the reason.
Seriously, get some starter fluid for the first start. Not ideal, but at least it’ll catch, you’ll get the break in started, and the next start should be easier.
I have no explanation for why the new magnet would be “bored way too big,” as the magnet bores are identical for both (the crankshaft diameter for all Leopards is the same). Wait, maybe it’s the trigger for the X-30 engine and they sent (or you unknowingly ordered) the wrong ignition kit?