I came home to several burst pipes in my third floor, in these single digit temperatures. Yeah, I know. Turn up the heat next time!

I have Slant Fin baseboards (Fine Line 15), and have several slits in the copper fittings, in addition to burst pipes in the return lines that run above the fins.

Questions:

Any way that the heating elements can be salvaged? The ends are flared, but can I replace these with 3/4 couplings?

The pipes come from behind an unheated knee wall. Is it safe to assume that the areas where the pipes burst are the only leaks I have, or will I be looking forward to chopping holes in knee walls to make repairs?

Are elements available separately, or do I have to purchase complete relacements?

I've soldered with MAP gas before, and believe I can sweat fittings to make a repair, but several things may sway me to replace with electric heat:

The plumber roughed in for Fine Line 30 when he installed the heat 15 years ago, realized his mistake, and connected these units anyway. He put a lot of stress on the pipes in doing so. Is it time to do things the right way, and replace these units with Fine line 30?

Another contractor I called suggested that NO pipes should be in unheated knee walls, and wanted to route EVERYTHING

"indoors" so to speak. I would go electric before I re do everything.

This is a third floor bonus room of my house, and gets used on weekends. I don't have much money to "redo" plumbing that was a poor design in the first place.

Is having the zone valve off enough to prevent more water from leaking when things thaw? Or should I cap a pipe upstairs?

Any tips would be appreciated.