@Merk issue, I'll try to dig out relevant threads from Tank-Net, but it seems israel now fields 3 active Tank Brigades, one with Merk IV, one with Merk III and one with Merk II (presumably atleast some uparmored as they appeared in the Lebanon war footage) and Reserve units (atleast those likely to get mobillised for things like Lebanon affair, not for all-out war with say Syria) do also already use Merkava's, so Mag'Ach's etc. are not likely.
As for the losses, most serious were due to IED's, as the massive IED's used by Hezbollah seem to cause most losses per tank.
Ah, here it is, this post is rather informative, linking two articles.
TankNet post
As for Kornets etc., I got impression appearance of top-notch weapons (Kornets, RPG-29) was rather rare and most of missiles were Saggers or comparable, most likely also the Iranian Sagger clones. In the same manner, most of RPG's were RPG-7V with equivalents of PG-7VM. Such weapons definitely formed bulk of captured weapon caches shown on displays. Not confirmed, but RUMINT tells that significant number of dead / injured Israeli tankers were unbuttoned at the time of hit and were hit by splinters/blast.