Team Sales is based on your division level and standing, as well as the main fan survey components (TV/rivalry game wins, cup standing and transfer list ratings, etc). Based on the information released on Discord and the forums about the nature of the merch bug, I don't personally believe that Team Sales was impacted by the bug, and $18.6k for a freshly demoted d3 team that's borderline playoffs doesn't seem unreasonable to me.
Homegrown & Locals is a %age multiplier on Team Sales, based on the percentage of your salaries that is from Local & Homegrown players. If you're fully home grown, that multiplier maxes out at 160%, with your salary ratios and posted Team Sales amount, the calculation for HG&L is correct.
Arena Sponsorship and Merch Store are flat values based on your arena design and merch store respectively, so those won't change and weren't effected by the Merch bug.
For some reason I missed Sadyrin when I was looking at your lineup earlier, but all three of your top players are making 10% of their salary in jersey sales, which is in the typical range for players with one or two top 10 rankings in the major stats for the league and no significant top-world rankings. Being down in D3 means your players are competing with 4x as many players for "top in the division" rankings, and will by that nature depress their jersey sales some. But even from what I've seen in the top level division, a player's jersey sales will max out at about 15% of their salary unless they're playing on a NT/U21 team.
So yes, I do believe your merch is in line with your current situation, and that you effectively got a refund you shouldn't have because they back-calculated the merchandise to compensate people with by looking at the end of last season (which I expect was substantially higher merchandise for you, with the higher division level's base sales of ~$25k, the extra amplifier of the HG&L bonus, and the jersey sales from the players you sold off at the end of last season).