There was very little difference between Highland, Lowland and English shopkeeper and merchant classes clothing by the 1840s and 1850s. Except, perhaps, in the matter of headwear. All men wore hats, but positions in society were easily identified by what was worn on the head. Labouring class chaps and most farm workers wore cloth (now called flat) caps, and this included lower-end shopkeepers and most household servants. Upper-end shopkeepers and upper level servants and some merchants wore bowlers. Most merchants wore top hats with even the height and quality of those adjusting with their social standing. Crofters and some farmworkers continued to wear a form of bonnet that has evolved into the Balmoral of today.

Scottish townies did not wear the kilt even at Inverness, the "capital" of the Highlands.

I think that may be disillusioning, but you said you wanted to do things more correctly than you were able to do last year. The best thing to do is to research clothing of the 1820s and 1830s London era, keep that as a style but go to a rougher form. The clothing styles of England and the Lowlands had changed what folk wore in the Highlands, but there were no surplus pennies in the shopkeeper class with which to buy the products of the new clothing industry. The result was that styles hung around longer and coarser cloth was used.