Your bluey-grey/yellow sticker is the correct cup shock. It should be part number 8200681125. The thing you say about it not compressing to the same amount as the old one is more likely to be a result of it being broken, it probably wasn't doing that when it was new.
By the way, I'm on my fourth pair of rears! They can start to leak after very little use in my experience, as little as 5k miles - yes! They are shockingly bad (like that pun). I'm not sure if its because of hard use on track or not though. Its probably no coincidence that its about a week or so after a trackday that I noticed my last pair, when only two months old, began leaking. Both sides within a few days of each other! And the pair before that had one develop the same shorter-travel (stopping with a "clunk) and a big leak, like you describe above, at just over a year old. That had been shortly after a couple of track days too. Touch wood my current pair has lasted a bit longer....but I haven't been on track yet this year!!!