For your too-thin-wall problem, just to make sure I understand is it this area here that is too thin? :





For putting in a fillet there, it seems to work ok for me but note that this length here is only 0.007 units:




So only a quite small fillet will fit in there, here's an example filleting both longer edges using a radius of 0.003 :



Is that going to be enough to solve it though or do you really need something like moving this entire face inwards a ways:



If so then by what distance? The length on the bottom part here is only about 0.045 long:



so there isn't a whole lot of space to move back by but maybe some?

- Michael