I agree with Maryhysong, mark and weigh as you go. Eggs should lose 11-13 per cent of initial weight during the first 18 days of incubation. If they are losing too much weight you can increase your humidity to slow it down or vice versa.
I would also send the breeder an email conveying concerns about the shells. At least that way if the result is poor then you stand a chance to get replacements or money back (if you chose to) At the very least, the breed would have some feedback about the product being sold.
The breeder should really offer to replace the eggs.
I have never hatched a porous egg successfully