Did you try
Mobipocket Creator
Or edit the EPUB in Sigil which is an WYSIWYG EPUB editor - see Download sticky here
https://www.mobileread.com/forums/forumdisplay.php?f=203
replace all '! ' (bang space) with '# ' (crunch space) - mask real exclamation points
replace all '!' (bang) with ' ' (space) - kill off those pesky bangs
replace all '# ' (crunch space) with '! ' (bang space) - unmask real exclamation points
save file
BR