I agree with Gonzo 1066 in that you have to consider the economics of it all, after all you did buy a CTD in the first place. If you were not going to want to keep it a long time, or put alot of miles on it, perhaps it would make sence to save the money and stay with a gasser.
I switched to Amsoil at about 15,000, now I have 300,000 on it.
You also asked about the by-pass filter, I beleive if you spend your money on better oil, you should get your money out of it by using it for its full life span, the by-pass filter system will allow you to do that, and both products ( oil & filters) will protect your investment in the engine. ( I like the Fritz by pass system )
I have been using an oil analysis, and have been able to get away with changing my oil at about 50,000 mile intervals, with filter changes in between.
I know I sound like an ad for Amsoil, but this is truly my experiance.
With oil changes about every 10 months, and little waste oil to deal with, I wouldn't use dino oil if it were given to me.
I suggest you educate yourself ( which you are doing) and decide for yourself.
Last thought... I find it interesting that Cummins does not recommend synthetics during break in, that suggests to me that they realise synthetic oil will reduce friction to much during that period and not allow components such as the rings to seat properly, based on that, when break in is finished, why would you not want to use the product (s) that will protect the best.
Pick a brand and go with it !
good luck