Can I DIY fix the broken main feeder support cable?
You can see right there where the steel cable is bonded to the lighter colored of the three service entrance wires.
Yeah, you lost a neutral.   This is when we get out the big font and say
This is a power outage. Call your power company NOW.
Normally these arise as “Hey, my appliances keep blowing up”... or “I measured 84 volts on an outlet” “check your other ones” “Oh, this one is 148 volts”.
But the funny thing about lost neutrals is people can take quite some time to realize they have the problem.
But yes, that wire is electrically “hot” - well, it’s near ground voltage if everything is working... but if you go up there and try to rejoin it, you’ll end up with one wire in your left hand and the other wire in your right hand, and the neutral current will try to go through you.
Of course, you said “feeder”.  That is a word with a specific meaning: it means a cable after the meter going between panels.  So supposedly you would have a house and a pole barn or something, and an overhead line feeding a subpanel out there.  But that would be 4 wires (with messenger as ground), not 3 as we see in this photo.
The specific name for this cable is “service drop”.
And the service drop is in the power company’s bailiwick, so they will fix it for free in almost every case.