Is it a weapon attack or a melee spell attack?
The spell summons a weapon, which then is used to perform weapon attacks.
- hunters mark doesn't work
As far as I'm aware it does. It adds 1d6 Fire damage to its attacks. Kind of odd how it works, but the extra damage is there.
On a side note, wizards cant learn flame blade from a scroll which is kind of shame.
No, as it's not part of their spell list. Just like Wizards can't learn Cure Wounds or Revivify from scrolls. Wizards can only learn Wizard spells from scrolls.