Sounds like a haulout and a mast drop are in your near future. I would not be sailing that boat with the deficiencies you describe, changing a through-hull fitting is an out-of-the-water job, or at least a tide grid one.
Your mast sounds like it needs a complete going-over, what you've seen is bad enough, leads me to wonder what is there (or isn't there) that you haven't noticed yet. Try to get a boat neighbour with some experience to look it over and advise you - you would be wise to engage a rigger for a proper assessment.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)