1. Not really, speakers tend to last very long and look at the huge market for vintage speakers.
2. No. Everyone has their own taste and plenty of great designs out there using paper woofers and silk domes and wood boxes.
3. SF post FS the speakers got a bit more modern sounding aka bright and lost some but not all of their musicality.
I can't really answer the rest of your questions other than to say your Dartzeel amp should drive a pretty wide range of speakers. And matching speakers to room really depends on the specific room and speakers and also your expectations.