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Viessmann IDWH Vitocell-B 300 Leaking "fittings not tank"

Viessmann IDWH installed around 2014. Leaking top supply fitting for domestic water see pic green dot. System is hooked up to city water. Water pressure is 54 PSi no backflow preventer but has small domestic expansion tank ext30 size ? Tank temp kept at 127 so i guess 5 degrees above and below that. When going away twice this summer tank off and water off. Ok so it looks like a crack, did I tighten it to much installing it? Did it just crack over time heating and cooling, or crack when it was installed new and was sealed up with pipe sealing cord loctite 55 and pipe dope. So I Installed a new fitting with a lot less force. Old fitting was hard to get off, was almost thinking about cutting slit in side, was afraid of torque on built in tank fitting when removing. Ok clean old fitting and install new fitting great. No leaks made sure not to tighten to much. Two weeks later water in drip pan. I think ok need more tightening of fitting. Looking around to find and verify leak and it was a new leak from the plugged recirculation line cap ie not used so just cap. Again fitting has a crack and is dripping from crack. That cap and fitting was not on very tight at all, either the crack made it very lose or was not on that tight, like I was thinking caused the first fitting to crack. This time pull tank cover off and make sure nothing looks strange in tank. Look at pic of tank looks brand new and will last a lifetime for sure. By the way the cover alone must weight five pounds. Looks built like a army tank. I made sure to use a new plastic toilet brush to clean. That clean out hole is to small but I guess better than none. My arm was to big to fit very far into tank. I am sorry but who in the heck is going to take top cover off and pressure washing down the hole in some ones basement for maintaince every two years like in manual. Can't talk cost here but that would cost how much??? every two years in addition to two new gaskets. My 12 year old had skinny arms they did the best they could with plastic brush. After brushing and using a shopvac to get all the water from bottom of tank and repeat. Looks brand new see pic.

Sorry for the long back story, now for the questions.

Fittings are 1 inch brass . supply house for fittings ? 1 npt to ??? viessmann tank. I think they are really adapters from british to NPT?

One pic show different fittings IE from different Viessmann IDWH. It being 2014 that was around the new low lead law for brass fittings. Does anyone know if any from pic are new low lead, or where they all to begin with? The two on ends in pic are different from ones in middle. The tank has built in france on label. I am think the fittings might be to go from Britsh pipe thread to NPT? Any thought if this is in fact true? I am going to have to get new fitting to be sure i am not using fittings that have more lead than the law allows.

Ok so looking on the web at what might have cause cracking some sites say the following.
Stress cracking
Don't use hemp, I used loctite 55 pipe sealing cord with pipe dope like in installation Manual. Looks like modern version of hemp.
Don't use pipe wrench. I Did use pipe wrench with three points on fitting like taught. I don't know would a real pro have a open end wrench that big.
Cause by cloride taking zinc out of fitting over time.
Fitting tightened to much use tourqe wrench, again i can see it on refrigeration lines but not for this big of fittings.

Anyone seen this?

Thanks for input on cause and supply source for new fittings.