Hopestation, I wonder if you are not quite getting the idea of packages under linux ?
Really sorry if this blindingly obvious but just in case ....
To install Lazarus, you first must have installed FPC and FPC-SRC. The latter two are dependencies of lazarus and separate packages. They probably have dependencies of their own, build tools etc. No basic reason why someone could not make a deb or rpm that contain everything but it would not be consistent with the Linux model.
If you use one of the GUI tools that gets the package from an official repository, it will automatically resolve those dependencies for you. But right now, those official repos don't have L1.8.
So,
https://sourceforge.net/projects/lazarus/files/Lazarus%20Linux%20amd64%20DEB/Lazarus%201.8.0/ has those three packages. A manual install means dependancies are your problem. You would first install FPC, maybe resolve any dependencies there, and then FPC-SRC and then Lazarus. In that order ! I have done it, maybe four or five times recently, and everything worked fine.
My 1.8 Ubuntu install has chm files (including lcl.chm) in /usr/share/lazarus/1.8.0/docs/chm/
My guess is your problem is related to your reluctance to install as the package maintainer intended, in /usr (why not ?) - the files will have ended up somewhere and my guess is Lazarus cannot find them. If you have a bit of time, maybe do, find / -name lcl.chm
Then, of course, you will need to tell the chm viewer where you (hopefully) found them.
Davo