1. Ref the hydrogen problem (leak in the Tail mast quick disconnect area), TBF that’s not a problem confined to SLS, pumping LH2 is fraught with difficulty and it’s a problem of a type that has popped up regularly ever since hydrogen was used as a fuel… even on Apollo 11 a crew had out to the pad shortly before launch to torque up a few bolts to stop a leak in a pipe used to top H2 up in one of the tanks.
2. Atmosphere in Orion cabin : Hard to find a definitive answer but as I recall it with Orion it’s variable.
AFAIK the idea is to launch with the cabin ventilated with air at 1 bar but certainly on missions where there is going to be an EVA (see edit) it would then gradually to morph to (?) About 2/3 of a bar but oxygen rich (30% 02).
The thinking behind that is that is to reduce the time spent pre breathing with 02 prior to EVAs, where you need to be at low pressure but high 02 to keep the suits flexible.
Pre- breathing pure O2 to get the N2 out of the body is needed to avoid decompression sickness and ISS experience has shown the pre-breathing times if you start from being in air at 1 bar can really really extend EVA prep time…
(The above of course is one of several reasons why early US spacecraft went with 100% 02 low pressure in flight, the foul up was using 100% in the cabin on the pad at 1 bar)
ETA: I missed a step…The EVAs of course will not be ex-Orion, they will be ex HLS on the Lunar surface…the thinking
AFAIK and ATM is that HLS or the gateway (if ever built) will be low’ish pressure, O2 rich, cabins for the reason previously stated, so Orion will have to match that for docking.