fixing embedded links in EPUB

[helpplease]

I have new to mobilread posting and creating EPUBs so apologises if this post is in wrong spot.

I have created an EPUB from several web page(s), all good except the 500+ embedded links all need to fixed. The text is heavily referenced to footnotes, end notes, and cross reference within title. It is a technical text.

Currently, if I click on the link, it forces me to relogin to where I obtained the chapter, sign-in, then takes me to online reference. Rather I want it to take me to the reference in my new ebook (epub).

Can I fix this in Calibre, using the editor?

embedded link is, say for bibliographical item 18 is currently
https://www.domain.MY ACCESS PROXY blah/view/[online book reference]/[online chapter reference]-chapter-1-bibItem-18

embedded link, correctly, I know I definitely need to remove MY ACCESS PROXY section.
How do I determine what else do I need to remove/change (I do not know xhtml)?
Assuming correction is a similar pattern, How do I easily edit 500+ links?

Thankyou for any ideas of how to proceed.