If I submit to the Angel Guild, will I be obligated to only work with Angel from that point forward?

Submitting to the Angel Guild does not lock you into any contractual obligations. The submission agreement does state that you will allow Angel the opportunity to negotiate a deal with you in the event you pass the Guild, but no contract is established at this point. In the event that you do pass the Guild, Angel would review potential distribution or licensing options with you, including potential third-party deals, before moving forward.