Oil and Excess Pressure in fuel

[HAULNTX]

Second update. Once again I'm learning all of this as I go and most of it is from this form.

On Thursday I pulled the valve cover to replace leaking injector no5. When I pulled the cover I noticed the injector cam and rollers had wear and pitting that was not there a couple weeks before. That sent me down the rabbit hole of finding out that the crankcase filter was getting clogged up way to fast. I haven't even put 10K miles on this truck but I've changed the filter 3 times. The last time I pulled the filter out I noticed the green slime and thick sludge and it had a lot of water collected in there. Going off this forum yesterday I pulled the oil pan and as soon as I did that I could already see coolant drops. Without even pressuring the system I could tell no5 cylinder was leaking from the liner. I pressurized the system last night and I let it sit over night, but at this point I don't think that was even necessary as I could see it draining down without even putting pressure to it.

At this point I'm going to go ahead and do a complete inframe, but as I go I will have some questions.

First off the head that I replaced a couple weeks ago, before I knew it made a difference, isn't a cummins head like the original one is. The original head was replaced due to no6 injector cup leaking coolant. Since I'm already pulling the head again, should I have the original head rebuilt with new injector cups or just leave the current aftermarket head? This truck has the CM871 and it only has 310K miles total on the truck. I believe around 9-10K hours. Also I currently have diesel and oil samples sent off and I'm awaiting test results. I really appreciate all the helpful posts from everyone it has made all of this process so much easier because of the info y'all put out.