a. There is no conversion of foreign licenses to FAA certificates above the private level (except one issued by Transport Canada). Since you already hold a FAA commercial your foreign license is irrelevant.
b. Since there is no process there is nothing to change.
c. The only way to get a FAA ATP (except the TC conversion) has always been to pass the written and the checkride. In order to do the checkride in an aircraft requiring a type rating you would also have to undergo a training program in that type aircraft and have a record of training and an instructor's sign off that you are ready for the checkride.
I don't know where you found the price for an ATP training program, I haven't seen any published yet. Given that you can get a B-737 type for under $9000 and the ATP training program requires much less time I'd think they would be much less.
If you think you will be able to do a FAA checkride in the next two years complete the written before 1 August.