Calm down. As previously mentioned IB move their aircraft around the network quite a bit. Needing to send the 346 due to higher demand on another route, e.g. NRT, means that another aircraft will operate your flight.

We've also mentioned that the 332 has had small updates and is IMO slightly more comfortable than the other aircraft, but it is much of a muchness. The seat pitch isn't below 30" on any longhaul IB aircraft.

Turbulence does not depend on the aircraft type (well, not depending on A330/A340 at least) and again the flight crew will do what they can to minimise turbulence.

A330s are not exactly old, those airlines phasing them out could have been operating them for over 20 years whereas as you state IB has been operating them for a year. Others may have replaced them due to age, capacity, fuel efficiency or a bunch of other factors.

I think you should just purchase your ticket and enjoy your flight before the price goes up, as you have been overthinking this for several weeks now.