First of all, the second burn @ 8x seems perfectly fine. Nothing out of the ordinary and it should be a working disc. The errors are not too high any ANYONE who tells you they are needs to quit PIE/PIF scanning and stop giving bad advice.
Second of all, if anyone tells you 4x or another speed is the standard and not to scan @ whatever speed you want, they are wrong and also need to quit if they think they are right. Home scanning is not in any way whatsoever considered a professional method of testing media and the results of home scans do not equate to how well it will play back. So scan at whatever speed you want - but if you want to compare results with other people or your other burns, it's best to test at the same speed to get a good comparison. But just for your own use, there's nothing at all wrong with 8x scanning or even 16x if you feel like saving time.
You can use scanning to give you a very general opinion of which writing speeds/media perhaps work best in your writer. For example, if you burn a verbatim @ 16x and there's 20000 PIFs, big red clumps everywhere and everything else looks ugly, then that speed is not good for your writer. If you burn @ 8x and the PIE/PIFs don't go ridiculously high (I mean like in the millions for PIE total and more than 5000 PIFs) then it's pretty clear 8x would be better than 16x for your writer.
But if you think one scan with 76 total PIF and 9000 total PIE is going to work better and last longer than a disc with 760 PIF and 90,000 PIE, you could be very wrong.
One last thing, your drive does not seem to be going bad, the verbatim you posted are not fake, and your burns seem perfectly fine.