I'm confused. Our hapless homeowner starts out with "I just finished installing a Monitor MZ25S Boiler" and ends up with "Lastly, don’t assume I am not doing things correctly and cutting corners. I have received a permit from my local building office; I am using the largest, most reputable, local plumbing supply business in my town and am working with a single sales person at the business; I am working with a local master plumber who has over twenty years boiler experience; and, tonight I have an appointment for an HVAC engineer to come troubleshoot my system and confirm whether a buffer tank is necessary for my system."
Which is it? If you "did it yourself" then you might have planned better...thus my time proven mantra. If you are hiring experienced plumbers or going around them direct to the wholesaler and you have an engineer, why come to a DIY site? I think the truth is in one of your meandering statements..."I couldn't justify hiring out the whole job. Ergo my decision in making this a DIY project with input as needed from pros. By the way, the 50k to 60k heating loss estimate came from one the plumbers (it does include both my upstairs and basement)."
It appears to me that you received excellent "free" advise and a fair price, from two experienced professionals - albeit without the benefit of a proper heat load - and chose to ignore it because you wanted to cut corners, lower your cost, get a better deal, etc. Had you really done your research and followed my various blogs, you would have started with a proper heat load analysis and wouldn't have been tempted by one of the 7 deadly sins, avoiding an obsolete, over-sized boiler and the understandably embarrassing position you are in at the moment. You are further mistaken by assuming that I have the time or inclination to belittle or bully you. I assure you I do not.
I consider your situation a teachable moment, as you are but one confused soul and many may benefit by your example and my sound advice.
I am really here to help those who will follow the wisdom gained of experience. I honor the spirit of the true DIYer; their courage, inquisitiveness and independent spirit. Unfortunately there is pervading prejudice among a fraction of the DIY crowd that frown upon any professional help or advice. I will not convince or persuade this lot, but hope to influence the more even minded that a little professional help up front, and perhaps at the end, will make for a safer, more efficient and longer lasting heating system.
Kudos to my esteemed colleagues, who tolerate my bad attitude and have patience when mine is gone.