well according to the fluff, the dark angel now has officially 6 successor chapters, from 2nd edition, they only had 3 successors mentioned, which were the Angels of Vengeance, Angels of Absolution, and Angels of Redemptions. These 3 in particular were mentioned to all be 2nd founding chapters, as in the Dark Angels only split into 4 chapters after the Heresy. The other 3 chapters now listed in the official codex are later founding chapters, with the concencrators and Guardians of the Covenant being unknown foundings and Disciples of caliban being founded in late m37. That being said, there is nothing that officially states the number of chapters founded in the second founding by any particular chapter other than the number founded by the ultramarines, which founded the largest amount and the salamanders which did not have any successors in the second founding. So, I feel that the dark angels, lost many marines if they were only able to found 3 successors at the second founding, as that would only be 4000 marines are less. They might have had over a hundred thousand at some point, but they didn't have many successors compared to other chapters. I think most of the second founding chapters founded per legion during the second founding would have been between 2-5 chapters, with the ultramarines having much more, as most of the other legions were badly depleted defending terra, or having a hard time rebuilding after Istavaan.
That being said, The terminator armors that the legions had, apparently are not the same armor designs of the current terminator designs, thus, those older armors are considered relics and terminator armor isn't unable to be created, it just isn't created as fast as the more mass produced power armor. Each chapter is only given 100 new suits when it is founded, and after that, they pretty much have to take care of those suits unless affiliated with a forge world. That being said, some chapters, like the parent chapters may have an easier time aquiring new suits if they suffer a loss of some due to a conflict like the battle of armeggedon. Outside of that, I would assume, Mars stock piles them for when the creation of new chapters, and only then do they let go of large numbers of Terminator suits, while Power armor is handed out to marines like candy (at least certain marks). Either way, the armor of space marines are taken care of, repaired, and blessed relics, and the chapters techmarines probably take care of those suits of armor. I would also assume that after a battle, if the apothecaries go and reclaim the Gene seeds, the techmarines are probably out collecting those suits of armor to take back to the armory for repair and recyling of parts. The only suits I would assume loss are the ones where they can't really reclaim and that would be the ones destroyed because planets were exterminated or lost due to losing a war, or sucked into the warp. I think they would recover all they could after a battle, especially if they won.