I think if the first tool you reach for is a cut off disk, you probably should not be doing any wrenching on bikes. And asking about what tool to use for a hex bolt also suggests the same.
at this point you have destroyed the spindle and will at minimum need to replace You need to remove the drive side crank, and then the bottom bracket as noted earlier. then figure our your replacements
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Life is too short not to ride the best bike you have, as much as you can
(looking for Torpado Super light frame/fork or for Raleigh International frame fork 58cm)