The kernel not booting thingy is probably due to wrong permissions of some kind purporting to the live kernel update feature. Since 3.19, the kernel is updated during the session, and the bootloader is refreshed in that process. If zypper can't access some files with full write access, I expect that an error like that would occur at reboot.
My guess is that by rebooting after a live boot, the install just snaps back to a working RO snapshot, which is what it's configured to do when there are problems.
OpenSuSE offers the possibility to ignore a failing startx. It may happen that X fails to start when the kernel modules have not been patched yet. Only use the packages by Siebert (sebastian-siebert.de), because those contain the latest patches on the latest fglrx modules. If startx fails, just Ctrl-Alt-F1 to TTY1, login, then snap back to the last working snapshot with snapper. You can list the snapshots, they are listed by number and have a description next to them showing what changes were made right after that snapshot was taken by the system (like zypper install or zypper update). To rollback, just enter as root "snapper rollback NNN" with NNN being the number next to the snapshot you want to rollback to (e.g. "snapper rollback 345", so without the "#" before the number, the hashtag is in the list of snapshots, but doesn't have to be put into the rollback command). Then reboot, and the system will be rolled back, and you don't lose any time, and can take a look at the debug journal for what went wrong.
I wouldn't recommend fglrx at this point in time. The performance benefit is marginal, and the extra features are even more marginal, because compiling the proprietary kernel modules into your kernel, disables the new amd HSA modules that are already in the kernel, that are made to work with the amdgpu driver that will come out very very shortly, in fact, any moment now.
Even when the amdgpu driver isn't there yet, you'll see that you get about the same fps in games like CS:GO in linux as you would in Windows (that's with fps_max 999 etc..., system set up as if it were for competitive play), and that's with the open source radeon driver in linux. Switching to the fglrx driver in linux, brings absolutely no fps benefit at all in CS:GO, but increases overhead, so the actual fps will drop a few frames in known problematic stages.
I get that not everyone is interested in HSA, and that fglrx might be what some users want to use, but it's also a dying development, and the open source kernel modules are the way forward with AMD GPU's in linux, so don't expect a great deal of effort from devs to keep the proprietary kernel modules patched for every kernel update, because every kernel update might be the last for which fglrx is even relevant lolz.
I would recommend uninstalling fglrx completely, and going for radeon all the way, to have a clean system for the next kernel upgrade, which will offer the choice of a completely new proprietary or the radeon driver, both using the open source kernel modules. When that comes, the proprietary kernel modules used by fglrx will be a potential source of trouble or loss of performance and/or features, so in my opinion it's better to get rid of them.