Change the engine? Or what?

DT.11

Hi. I’m a new member to this forum, but have been reading the posts for a few weeks.
I purchased my 2009z in May as a project car. It was misfiring (limp mode) and had a few noises coming from the exhaust (cat failure). I figured that the limp mode was due to oil pressure and an OBDII scan confirmed that, along with some other issues (p0011 and p0021) which I assumed were related. I replaced the gallery gaskets - top one was blown in multiple areas, but the bottom one was intact.
Starting back up and the oil pressure problem was still there, as well as the error codes. Nissan we’re no help, only saying they needed to open the timing cover and check my work before they could diagnose, so I am stuck.
I decided to check the oil bypass valve, just in case it was stuck open and I noticed glitter in the oil, as well as a few flakes of metal. These did not respond to a magnet, so I assume they are aluminium.
Is the engine shot?
Is there something else I should check before condemning it?

I have purchased another engine from a breaker, from a car that was stolen and had only done 60k, so I’m ready to swap the engine out. But I am questioning if I need to.
Help!