1. It'd take as much time as it takes for Susanoo to form around a Uchiha.Ok so for questions
1.How long would you say it'd take for me to fully form it during a fight.
2.if I struck an Uchiha's Susanoo with my chakra eating blade would it eat up part of their chakra and reduce it to lesser states such as the skeleton form?
3. Do the Keigoku weapons act as solids so I could cut through earth jutsu with 40 chakra and below? If they are solid and since this jutsu is F rank would I be able to slice through Forbidden rank solids/summons even if I can't absorb all their chakra. And I'd be able to cut a ninja in half with a swipe of the blade as well then?
4. Maybe I'm just not seeing it but is their a turn limit on use?
2. Hmm. That's a good question. I'd have to do more research into this one before giving a definite answer.
3. Yes, the weapons are solid and corporeal, possessing a full form, meaning they would do damage to a foe and can be used offensively or defensively towards an object, the same traits of the Obi are present. As most F ranked attacks are composed of chakra of 50 and higher, it's rather difficult to state the usage of this most times against a Forbidden ranked. If the Forbidden jutsu is composed of two halves, similar to the Mountain Smash jutsu, which has two large slabs of earth on each side, then the chakra is logically split down the middle, and would be capable of absorbing. If the chakra is in one solid form, then that would be an offshoot of your 2nd question and I'd have to look more into it.
4. No turn limit, but it does take 20 chakra each turn so until you decide to end it, or you run out of chakra.