Is it possible to somehow create a copy (an image) of a heavily cracked CD-ROM (but not broken in two)? Hopefully without damaging DVD drive...
Unfortunately CD 2/4 of Polish version of Planescape: Torment game got cracked...
If the encoding material (the, usually aluminum, reflective foil layer) is damaged, then you're probably out of luck. Otherwise, you can reinforce the backside with a label and mend the crack surface using standard CD repair techniques—e.g. applying resurfacing solution and putting into a heating/polishing unit. Here's another crack repair technique using scotch tape. Other repair techniques are discussed here.
As a last ditch attempt, some people have successfully recovered data from unreadable disks using cdparanoia (FOSS) or Exact Audio Copy (freeware). If these two apps can't read it, then it's probably gonna be more effort than it's worth to recover the data.
Though this should be a lesson to you to rip and/or back-up your purchased disks first thing in the future. I personally prefer to rip an ISO image and use that exclusively while I keep the original disc in storage as a backup. With UMDs (PSP games), this greatly reduces load times and also eliminates wear-and-tear on the original optical disk.
(I know the legality of ripping CDs/DVDs is in question in many countries, and software publishers will argue that you only own a license to play the game, not the actual DVD/CD. But most game publishers still aren't going to send you a replacement disc if yours gets damaged or is lost, so it's up to you to CYA.)
Losing a copy of PS:T would be a great loss to the world!
Recovering with ddrescue
I suggest you attemt to use ddrescue to recover what you can from the disk. If you run *nix it will run natively and is likely in your package manager or what have you not (macports?), otherwise it's included in many Linux live disks, some are listed in this thread.
You should have a look at the ddrescue manual, but a basic example (Example 3 in the manual) for recovering a cdrom is
You might want to add the option
You should then end up with an "iso" image of the disk, which you can then burn to a new cd-r or use with some disk emulating software.
Reducing the cdrom speed
As @ChrisF mentioned, spinning a damaged cdrom up to high speeds might not be the wisest endeavor, and it certainly won't help the rescue effort (it's generally easier to read the text on slow moving cars, right?).
I have no idea how to reduce this on Macos, but mot Linux distros let you use the eject command to reduce it, like so
Unless I'm very mistaken, a cd speed of
You probably want to choose the lowest available speed. Make sure you do this before you try to recover with ddrescue.
Unfortunately, there is a very real danger that you will lose some data in this process. This might have different consequences, though I believe DRM complications won't be an issue, general data errors might be a problem. Bit errors in textures is not really a big problem apart from looking bad, but damage in the binaries might be fatal. Assuming you can install at all, you might be able to extract non-broken files from the GOG.com release of PS:T (English, available at 10 USAian bux), although that would likely be a major undertaking. Alternatively, you might be able to copy savegames between the versions to play through broken sections. (This is just speculation on my part.)
About the physical aspect of the recovery process: one thing you should worry is that the cd spins at a very fast speed, and it might end up "exploding" inside your drive, releasing the fragments and destroying your drive... and destroying your CD, too, of course.
So, before doing trying the recover, analyze your CD and see how bad it looks. Even small cracks can propagate in a very intense way. And you know that the data is stored in the bottom of the CD. So, you might add something at the top of the CD, creating a new layer with some material to provide physical integrity to your CD.
For example, a thin layer of some plastic glued to the top of the CD. Remember that CD is made of plastic - polycarbonate, and you have to choose an adhesive that sticks to it, but without causing damage. For example, think of those paper labels that are applied in home-made CDs.