It is not so much that nobody knows as that all of this info. is available in documents on the Apple website that detail all of these minutiae. Look up what you need to know before asking here; you will almost certainly get a faster answer.
However:
1. The 150 is meant to have a unique power supply, and Apple warns of danger to the machine if it is not used, but I doubt that use of another 1xx series adapter would make much difference. I have run a 150 from a 145's adapter without problem, but owing to the warning, switched back to the proper supply once I saw that I had made a mistake.
I do not, however, have all the model numbers of Apple's power supplies stored in my head, oddly enough, so am unsure what machine an M5651 belongs to. Those documents, however, will tell you if you'd care to look for them.
2. A great many powerbooks will run from an early Duo M2693 (a 24v supply). I have run a 12" Wallstreet from one, so a 1400 should be fine. What would be likely, however, is that it would not charge the battery terribly quickly. It is also possible, one assumes, that the ps might fail under load, as the 1400c oem ps was presumably a 36w unit. (The later ps for the Duo 280c and the 2300c were both 36w units, by the way.)
Best of luck with it. 1xx series power supplies are notoriously hard to find, so nobody around here is likely to give one up without hesitation. You may be stuck with whatever you have already. A ps for a 1400 is much easier to find, as units with the requisite plug are still manufactured and readily available from our Chinese friends on ebay for a small sum.