Seems to me a good solution would be to stop using the PS4 and only use PC. You could accomplish this a number of ways with your back:

1) Get a controller for your PC so you could play laying down (possibly wireless would be best?)
2) Get a M/KB "tray" to lay across you while you lay down.
3) Get a reclining chair (most expensive option, though not having to buy a second copy of FF14 would help offset maybe)

Just a few suggestions. I'm sure there are other things you could try too.