Dyneema is a high strength fibre similar to DuPont's Kevlar. The fibre is used in rope, safety helmets, medical devices and anywhere else where tensile strength is needed. But at the end of the day its an ultra high length polyethylene chain - meaning that it will melt and burn like PET as would the elastane and the nylon in the jeans as well.

They will likely wear harder than normal denim but your weak points are likely to be other parts of the fibre mix, denim weave and stitching. If I was riding a motorcycle I would prefer to rely on a a specialist suit rather than these jeans because its as much about the engineering as the ingredients.

I am a big fan of drizabone jackets - different cut to your Barbour

How cold does it get where you live? How wet does it get? I live in the UK where we dont get much snow. I use a goretex shell and a polartec fleece, if it gets really cold I use a down jacket inside the goretex shell instead of a fleece. Like others have said I would recommend Patagonia, though it can be harder to get in some European countries. Another brand would be Arc'teryx as they provide a great service repairing older jackets. My current set of goretex shells: I have one from Arc'teryx (with more of an tighter fit which I use with thinner fleece mid layers and one from Nike's ACG range which has been surprisingly good (and can fit my down jacket mid layer underneath). I mostly use north face fleece jackets as a mid layer and use a Mammut down jacket as a mid layer when things get cold.