Contracts are difficult as you point out. Precisely why he needs to focus on OK statutes. UCC provides many general and specific provisions, but depending on the lease it can go from relatively easy to complex fast. Also, UCC may not be the governing body since it applies to many transactions(focused on goods), but not all. I don't want to dig to far because this discussion could go on for years, but he needs to find a way for his lease agreement to be fixed in a timely and financially beneficial way. The intent of the landlord may have been good or bad; we don't know his state of mind and why he worded it the way he did. The problem is the poster is looking at a possible $1000 debt. It's likely the landlord already has a months rent(depending on OK laws) so he(poster) may be forced to take the landlord to court. The amount of time and money may not be worth it, precisely why I hope the JAG can assist.
§24. OFFER DEFINED
An offer is the manifestation of willingness to enter into a bargain, so made as to justify another person in understanding that his assent to that bargain is invited and will conclude it.