Two hours at SVO is sufficient. Five hours [at any airport] would try my patience.

Y on SU is fine. If on an A330 SVO-NRT, seat comfort is normal (not cramped), and food is edible. My sense is also that, in light of the state of the Russian economy, SU loads are down, meaning that you may have a good chance of being able to spread out. The AMS-SVO segment should similarly be fine--no less comfortable than KL, IMHO.

My sense is that the SU routes to Asia end up with a lot of bargain-hunting students transiting to/from Europe at certain times of year.