We do have M6 carriage bolts that are 80 mm long, check out the Thule Xadapt3, part # THXADAPT3, which comes with eight, 80 mm, M6 carriage bolts.
The wingnut that you referenced, Thule Replacement Wingnut, part # TH04877, will work with the 80 mm carriage bolts # THXADAPT3, and the 75 mm bolts, part # TH915-0675-11, and # TH10403. view full answer...
A Dexter 2,500 lb axle uses hubs that have inner and outer bearings of L44649 like the part # 8-257-5UC3 which has a 5 lug bolt pattern or the # 8-173-16UC3-EZ which has a 4 lug bolt pattern. These both come with bearings and seals as well.
For brake assemblies you'd want the part # 23-47 for the left hand side and # 23-48 for the right hand side and you'd be set. I attached a help article link on adding electric brakes to a trailer for you to check out as well that I think you'll find... view full answer...
For your 2014 Volkswagen GTI you can use trailer wiring harness # 119250KIT. This is a hardwire kit. A T-connector style is not available for your GTI. view full answer...