Your limb lengths are why you might go from 135 to 405 rather than 225 to 495 over the course of 10 years, but they are not the reason for being stuck at 185lbs!
You kind of lost me here. Is this a fact that, all other things being equal, an absolute beginner with shorter limbs will be able to start w/more weight than one with longer? I can see the advantage for smaller limbs in terms of making gains but I wouldn't have thought that it would affect beginning levels of strength.
If you took all untrained people and tested their initial max lifts then there would be surely be a correlations between different limb lengths and weight lifted, especially weight relative to bw. Limb lengths, limb length ratios, bone structure, and differences in muscle insertions will make a large difference between the strength levels of untrained people.