No, no and no.
You got it all the wrong way
Check the manual, and the addendum, and think about it:
- Check for repel is done when the rolls for the
attacking unit are made.
- Repel is 1 damage point
fixed. No special weapon properties are taken into account.
=> There's no 'repel attempt', there are only 'attack attempts vs longer weapons'. Each unit has a chance to get repelled for every attack it makes (if it uses shorter weapons than the target).
If the target has multiple weapons, greatest weapon length is used for repel calculations. Therefore it doesn't matter how much weapons you stuff on your Nata.
This leaves the question - what do Flaming Weapons do?
In case of the defender, nothing.
In case of the attacker, I'm not sure. They (and other secondary effects) should not add a full attack, but an additional damage roll, so there's no additional repel roll. (flaming weapons don't have a length, you know). Otherwise, any blessable multi-weapon unit would kill itself quite quickly against Light Infantry, what they don't.