Because methane is flamable and the other anaerobic gasses generated by sewage are toxic enough to be fatal, CG regs require all waste tanks--gray water and black--to be vented...not only vented, but vented to the outside of the boat. I know...you said the pumpout boat comes often...but sewage generates gasses that can expand and create pressure. That pressure needs an escape route that isn't a blown out tank fitting.

And btw...all your hose connections should be double clamped too. Especially in an unvented system, a single clamp connection is weak point.

CG would cite you for the unvented tank...a good surveyor would nail you for both. Hard to tell from the photos...but it doesn't look like you have a vented loop on the head intake. That one is necessary when the toilet is below waterline. Goes between the pump and the bowl, not between the thru-hull and the pump.