Bernham Steam Boiler worked when we bought house last month - now it doesn't

We closed escrow on a home in MA 3 weeks ago. During our home inspection in July, they tested the 1991 Bernham steam boiler and found it working - took photos of temp readings by radiators. We moved in two weeks ago and system won't fire up. Called plumber, first thing he did was turn water to fill tube (it was about half full) and water started gushing from below boiler tubes. He said system is cracked, not fixable. We want to convert to whole-house heat pump and have started the Massive process (energy audit done last week) but it will probably be a couple months before it's installed (insulation, electrical have to happen before). So, we are in a dilemma. I will be babysitting my two small grandchildren starting Nov 14 and am worried about space heaters being our only heat source.

My question - this system was working with the water level lower. There is a black line drawn on the water tube above where the water was - we think it's possible that's the line to stay below so it won't leak? Is it possible the crack is above that line, so if we keep the water below the line it'll work for a couple months? There's obviously another reason it didn't start though - and my husband thinks he heard a click when flipping the power switch on that indicated a problem in the switch.

I understand without seeing it, there's no way to be certain what the problem is - but is it possible to use this temporarily if it has a crack? Or, is it done?

Definitely been a difficult move so far...thanks for any help/advice.

source https://hvac-talk.com/vbb/threads/2243640-Bernham-Steam-Boiler-worked-when-we-bought-house-last-month-now-it-doesn-t?goto=newpost