Owww! My Eyes!
What has been seen cannot be unseen!
1st thing do not have the water turned on until that PVC Supply has been fixed.
That is a disaster waiting to happen.
Many places PVC isn't even allowed inside the foundation.
The washer standpipe looks more like a drain without a trap and vent. After that has been properly plumbed yes you can secure it with clamps and tapcons.
Your venting plans sound on target as well as your uV protection plans for the PEX.