Just a brief google search revealed numerous PADI centers in both FP and Madagascar. So that information is incorrect also.
The diving in French Polynesia is all about the Tuomotos - Dolphins, masses of sharks, great hammerhead mating aggregation, whales - unfortunately you will not be able to secure work there as you are not French and there are no loopholes. Also FP adheres to CMAS certification not PADI so without being a CMAS certified instructor and marrying either a Polynesian or French citizen - you're out of luck. I rate the Tuomotos as probably the best diving in the world.
Madagascar - nice for a topside visit, diving is Ok, Did not see any Americans working anywhere - all French due to Madagascars prior status as a French overseas protectorate. Also most dive shops close during cyclone season. If you tried to work there you would probably be paying more in bribes weekly than you would earn and be prepared to be kicked off the island or imprisoned according to the polices whim. It is not a politically stable country, expect military coups and be aware that lynchings have and do occur should you upset the locals. Madagascar is also CMAS.
PNG - LOBs that are in business have local Papuans working on boats, there are no "resorts" offering courses due to regular tribal violence - Tawali got hit again yesterday with all guests "kidnapped and robbed" Which is unfortunate because I'd rank PNG as the best diverse diving in the world. You'd stand a better chance of securing work as a private security agent than in the diving world if you are ex military - if not, forget that too. Even in the capital Port Moresby you do not venture out of the expat gated communities without a PSA and if you do drive you keep your car doors locked and do not stop for police because they are just as likely rob you as the locals. The two supermarkets are surrounded by barbed wire fences and the security agents will only raise the boom gate to let one car in at a time.
Solomons - Uepi is amazing diving but again, very little job options as they are quite hard to get to so there is no great volume of divers so I'd imagine the owners would have little interest in an "outsider" rather than a known person who has a relationship already established with them.
Tonga - whales are about it - not a lot of reef and whale interactions are done snorkelling not diving.
Indian Ocean - Maldivian political situation is dodgy but I haven't dived there so cannot provide any info on the employment of foreigners situation. Thailand you would be working illegally but plenty of people do it between "crackdowns" - either marry a Thai or have a Thai business partner if you want to be legal.
Raja Ampat/Komodo - guides are all Indonesian. If you have experience as a Liveaboard cruise director you may stand a chance but the process of obtaining a KTAS to work legally there is quite lengthy.
Sorry to rain on your parade. I do know of a job going in Vanuatu - pretty pedestrian diving but Vanuatu has a foreign affairs/aid relationship with Australia so all the non Ni Van people on Vila and Santo where diving is are Aussies running the operations.
Not sure if there is any diving there but American Samoa may be worth a look. Guam as a US Territory may also be an option and there is good diving there.
Good luck!