Update on my TT causing distortion at higher volume

CDPs nearly always require much more attenuation than phono, because their standard signal voltage output is nearly always at least 1V and more often 2V. And it’s the same regardless of the program material. Whereas phono voltage output is rarely as high as 1V and varies from one LP to another, depending upon how the recording was made and by whom.  And of course it also varies depending upon the cartridge driving the phono stage.

What made me think you just might be running your MM into the MC inputs of your phono is your mentioning that the volume jumped way up when you first auditioned the MM cartridge, after having listened to your MC.  That suggested to me you might have connected the Ortofon to MC inputs.  Otherwise, the signal output from your phono stage, for an MM connected to the MM inputs vs for an MC of proper output connected to the MC inputs, ought to be about the same, in terms of the resulting SPL for a given setting of the attenuator on your linestage.

First, by owning and listening to one MC cartridge and one MM cartridge, you will not learn "the difference" between MM and MC. You will only learn the difference between the two particular cartridges.

Second, according to the internet, the E-glo has provision for both MM and MC types. Just be sure you have connected your Ortofon MM into the MM inputs. If so, then check the capacitance loading which is adjustable on your E-glo. You guesstimate total capacitance load by adding the capacitance of your phono cables to the inherent apacitance of the phono input and the added load capacitance at the phono stage (which is the adjustable parameter on your E=glo). If the total capacitance is much different from recommended for your cartridge, that too can cause distortion. Load resistance should be 47K ohms or higher.

Since the SLP05 is a linestage, I have to wonder what you’re using for a phono stage. Could it be that you’re driving a high gain MC phono stage with an MM cartridge (the Ortofon Red)? This would inevitably overload such a phono stage and cause the objectionable distortion you describe. If not, then you just need a better cartridge, and that’s not hard to achieve, given your present starting point.