Help with a hot water fed home radiant heat system

It has been a long difficult way to get to this site, but I think I will find an answer.

My in-laws house was built in mid-1960s. It is a ranch house produced from architectural drawings purchased through the mail. One owner previous to my in-laws in purchase in late1970s.

After my mother-in-laws passing, my brother-in-law has lived in alone for a decade. With a bit of a hands off, princess mentality, he has just trused handymen inherited from parents or recommended by housekeeper.

Well water with high iron content.

A single tank "descaler" which may be passed its recommended replacement date was added in the last decade. It was installed by the oil supply company.

Heating is supplied by an oil burner furnace. The heated water runs through 1/2" copper pipe. At heat distribution sites in rooms the copper feed pipe is fed through a 1>3 iron splitter that connects to three copper pipe with aluminum fins for length of wall recess, into a corresponding iron connection. A short bridge of copper is connected to an iron T fitting. From the top of the T an Italian, patented, chromed, iron self-bleeding valve, is mounted on a 3" stem of threaded iron. The valves release is set by turning a threaded stem of which the internal end is a conical point that closes into the internal seat.

On several of these valves, the adjustment screw was frozen in place with a white corrosion that dripped down over piping.

The house is zoned in two. The thermostats control electric brass valves mounted on the main pipes leaving furnace.

There is a single insulated 18 gage copper wire that travels the length of pipes in basement. The wire is separated from pipe by ~6 inches held in place by being threaded through a plastic button on a metal spike driven into floorinf joist. The wire will connect to a brass union fitting that connects long pipes. I found one such fitting to have a small plate warning against removing ground.

The furnace was replaced ~10 years ago by the company that has supplied oil for my inlaws for over 60 years through two houses and a business.

The pressure release valve directly from furnace heat exchange had failed four times in ten years (that is know of). There is no alarm. It in in basement. Water travels from utility room through double length garage to outside. It has flowed for several days with my brother-in-law oblivious upstairs. The flowing water will be red with iron oxide.

Past floods have destroyed furniture stored in garage and raised humidity high enough to initiate surface rust on tools and car undercarriage.

The expansion tank has been changed at least three times. (The removed tanks have been tossed into crawl space behind burner. The iniitial one replaced with same size, before swapping to a larger one. The discarded tanks had no obvious defects.

Those patented valves have failed in the residential spaces. A leak will start as a trickle. In a room with wall to wall, it will go unnoticed for days. The valve in kitchen sits on what haf been three inches of iron but is now is an assemblage of layered scales of rust that sweats. A past leak stained the linoleum flooring and initiated rot of the plywood subfloor.

This past winter I had to call the oil company when the entire system stopped working. The third generation owner, a man ~40-50, showed up himself. He checked water pressure. While he was in house, I asked him to replace several valves ($100/pc).

By this time, my online research had enlightened me about galvanic corrosion. I asked the man. He wasn't familiar with the term.

I need to have an idea of what is wrong before I can speak to my brother-in-law and attempt to find a competent person for lasting repair.

TThanks to all in advance for any assistance.

Chris