There isn't a wheel caster available for the etrailer powered jack that you referenced. In general they aren't options for powered jacks too so we don't have any similar options that would have that feature. So if you wanted to use this jack and still have ability to roll trailer around you'd need a dolly like the Rack'em part # RA20. view full answer...
The biggest wheel size with a 4 on 4 inch bolt pattern is the tire size ST175/80-13 like the part # AM3S101 that you referenced. This would be right at 4 inches taller than what you have now and would take up about 2 inches of the available fender space. view full answer...
When you replace the narrower AL KO brake assemblies and drums of your 3,500 lb trailer axle with the wider size of 10 by 2-1/4 inch using the assemblies # AKEBRK-35-SA and hub/drums # AKHD-545-35-K the hub face to hub face dimension would not get affected. You wouldn't be adding any width to your axle. view full answer...
I would go with the Taskmaster trailer tire part # TT53012C which is a 5.30-12 tire size because it is a radial which is preferred over the bias ply you have now, it has a higher weight capacity and speed capacity which will help prevent the blow outs you've been having as long as you inflate the tires to 80 psi when cold. These also have a 2 year warranty as well. view full answer...