Indirect Water Heater -Rusty Colored Water - Help me diagnose

I can use some ideas on an indirect water heater I'm working on. Trying to determine if this is sediment, or possibly a break in the indirect water heater coil from the boiler.

Indirect Water Heater/Radiators/Boiler:
Weil Mclain Gold 50 gallon water heater that's connected to a Weil Mclain boiler. This is an older Triangle Tube Weil Mclain Gold, not the newer style. This boiler is heating the indirect water heater, and radiators throughout the house. Water heater looks to be in great shape from the outside, no leaks. For the record, these indirects have no anode rods, and no drain.

Issue:
It sat for a while (Over a year+ with no use). Once we got the boiler back up and running it seems fine, no leaks after reworking the supply inlet, but the water would come out rusty after sitting for more than a few days. I went ahead and took the supply side, removed what was left of the dip tube, and did repeated draining and refilling from the top inlet port with an electric pump. I made a temporary dip tube that connected to a hose end so I could flush the water in with a hose and the water pressure, then used that same setup to drain the tank from the bottom with an electric pump. So it seems like it would be hard to still have sediment in the tank since I did this drain/refill multiple times.

First Gallon to domestic is colored:
If the water heater sits for a few days, the first gallon or so has a slight yellow rust color to it. It still not in full daily use so I'm not sure what happens if its used daily, but I'm trying to get to the bottom of it before its being used daily.

Pipes In/Pipes Out on Domestic:
The water supply line going to the water heater and output to the faucets is all new, so the rust water is either coming from the interior of the holding tank within the water heater, or worse, its somehow water that is coming out of the boiler water that heats the water heater coil.

Pressure:
From what I can tell, the pressure in the boiler is roughly about 12psi when cold. That number doesn't seem to change. I assume IF the coil inside the water heater had a crack, the water pressure in the boiler would be dropping steady. Its been warm so the system hasn't been running all that much, but I think I may plan to force run it and jack up the heat and empty the water heater completely at the faucets a few times strategically over a few days to see what that water pressure does.

Is Coil Cracked? Symptoms?:
If the coil was cracked inside of the water heater, would this in any way raise the pressure in the boiler? Or does it nearly every time drop the pressure as the water leaks from the boiler loop through the coil and into the domestic hold tank? I'm assuming the boiler pressure would always drop.

What to try next?
Can there STILL be rust/sediment inside that's causing this? I flushed this thing multiple times, and drained it from the very bottom. Maybe I need to pull the relieve valve and try to run water in the inlet and let it flow out of the top instead to see if that helps clear up any possible sediment/surface rust that may be on the upper components in the tank?

I called Triangle Tube and the support rep told me that its common for these water heaters to run cloudy for a while if they sit for a while, but that eventually it should clear. I was told the coils on these barely ever fail, but that the main problem is typically the holding tank gives out and the leak is visible. So chances of the coil being cracked are low I suppose, but I'm not ruling that out since I've flushed this thing so many times.

Looking for some last ideas to try before I cut this darn thing out and replace it.

Thanks for everyone's time and knowledge. You've all helped me through some tough things, and I appreciate you all and this community greatly.