Oh that is an extremely different experience that what I’m having! Chromecast works fine for me and i never have to restart anything and no problems with scrubbing either, just a bit slow on shows with a lot of episodes (300+). I have given my friends access to my server and most of them are using it just fine (sure with some issue now and then, as you said its not perfect). And in iOS with the alternative Swiftfin client the experience feels phenomenal!!
Yes! Usually the ones that come with the media are fine for me but i also have the open subtitles plugin to download extra ones in my language. There are no problems 98% of the time and the other 2% its just that they won’t load and I just have to select/download different ones.