I've only done a quick reading of the section, so take these answers with a grain of salt...
•For contacting a demon do I have to use a spell or will anyway of seeing a demon work?
Any way will work. For example, if there's a local church that's into demon worshipping, you could talk to them. Or to a wizard's imp familiar. Spells just make it easy.
•Can I offer up someone else's soul for benefits?
I don't think so. But under the Pact Insidious, you could probably offer to try and corrupt someone as part of your payment.
•Do you always get 9 points to spend? Or is it based off bargaining?
Based on bargaining and the value of the soul. A lawful good paladin will get more than an already evil assassin who's soul is going to be lost anyway. But if the PC is seeking the devil to initiate the deal, 9 is probably the max.
•If I find a loophole in the contract would I keep the benefits or would the contract become void?
The pacts already have a loophole, in that the person can atone. But on page 24
Hidden provisions in the contract revoke
the previous benefits if the mortal stops performing the
specified tasks.
You do the act first, then you get the benefit. Stop doing it, you lose the benefit. But I suppose it's really based on the wording of the contract - "If you kill the mayor, you get +1 STR"; you only need to kill the mayor once, not over and over again. But as a rule of thumb, I would say if you get out of the contract, you lose all benefits ("Hey look, I just resurrected the mayor! Stupid devil didn't see that coming!")
•Can I take the same reward twice?
I assume so. Take +1 INT twice for +2 to INT. Or take 2 feats. Or 3 extra spell slots.
•What is the worth of a soul?
It varies, but usually 7 or 9 points. If you're looking for a gold piece value, it's 60% (7 points) or 80% (9 points, projecting chart) of current wealth, so a rich king will be worth more than a poor peasant. Likewise, a 9th-level PC's soul will be worth more than a 2nd-level PC's soul. But don't think the 2nd-level PC can buy back the soul when he gets more money.
•Could I sell my soul to 2 Devils then when it's time to collect let them deal with it?
If you can get away with it. I would assume though, that devils have a method of checking on this.
•What about spell the let you repent? Like the one... Can't remember the nam... The lets you regain munk features after you did something non lawful?
I think you mean
atonement. It can get you out of the deal. But page 42
Strict prohibitions forbid the mortal from disclosing the
contents of the agreement to any third party. Though the
contract does not explicitly say so, these prohibitions are
meant to keep mortals away from meddlesome priests, who
can perform atonement spells to absolve repentant signatories
of the sins they have accumulated while fulfilling the terms
of the contract.
I would assume at the very least, this would cause you to lose the benefits of the pact.
