Congrats on snapping a highback. If you did it in the line of duty and not by being sloppy on an unload or skating, you should be proud of it. Otherwise hang your head in shame.
As for your other questions, you need to ask yourself them first.
Have you tried calling Burton? It's a wild idea out of left field, but as strange as it sounds you might find they have parts for Burton stuff.
As for it worth replacing your bindings. That's a question only you can answer. How much is it going to cost to fix them (call Burton)? How much would the new bindings you want cost? Is that difference in price worth it to you?
As for your other questions, you need to ask yourself them first.
Have you tried calling Burton? It's a wild idea out of left field, but as strange as it sounds you might find they have parts for Burton stuff.
As for it worth replacing your bindings. That's a question only you can answer. How much is it going to cost to fix them (call Burton)? How much would the new bindings you want cost? Is that difference in price worth it to you?