Speaking of th legality of the tag.
 

The legal definition of a tag reads that the the ball is not considered to be held securely if it jugged or dropped after the touching, unless the runner deliberately knocks the ball from the fielders hand.

For NFHS, maybe, not ASA, ISF or NCAA. NFHS doesn't define a "tag", it defines a "tag out" ;)

Then again, it is somewhat ambiguous since there is no time frame or particular action provided to determine when the tag out becomes legal.

Sorry, meant Tag out. The problem is it doesn't specify the time frame. I think this is where common sense should prevail, but .....

Common sense prevails when you just call the out when you determine the player had secure possession of the ball when applying the tag which is what the rule requires

If contact between the runner and the glove being used to make the tag causes the ball to dislodge, you have no tag.

If contact between the runner and the PLAYER making the tag causes the ball to dislodge (and assuming this contact occurred after the tag was made), you have a legal completed tag. Ditto contact post-tag between the fielder and the ground or something else.

Key is securely held. If a player looses possession of the ball while executing the tag, s/he obviously wasn't holding the ball securely. If the player makes the tag while the umpire has determined the ball was securely held and then the ball comes loose, it is a tag.

There is no requirement to pull the ball away or "complete" a tag for it to be valid and/or legal, whatever.