A couple of things have been posted here, mods, but what i found so far seems to have this or that uncertainty.
Also, from using (trying) software or online services that check for dead links on a huge site (5000 + links) i learned that most have limits or take forever.

So, my first question to anyone reading this:
Do you know of a good FREE dead link checker WITHOUT LIMIT somewhere to be found online???

My second question would be:
What is a good working dead link finding and manually removable mod for Links 2 (please point out the post) that can be run without slowing down the frontside (what the visitor is using and seing) ?

Have you tried Xenu Link Checker: http://home.snafu.de/tilman/xenulink.html

Yes, already some time ago, but it did not go through all, it stopped usually around 1500 links or so.
Maybe i did not find the right settings, but i actually contacted the guy that made it and did not get much further with it either.
My database has by now about 4000 real links.
I found an interesting one that works online
http://www.dead-links.com/
that went as deep as 2300 (if that is of use for anyone) and gives a usefully formatted report, but
i still don't have something that goes deeper, to 4000 or more, if you know anything that can be set on Xenu LS please let me know.
Thanks