Hi, I don't think your models are weak :], on the contrary they look very nice and very optimized
for example a bicycle is generally used on the background so it should be low poly, making it high poly like yours will
not be very appealing and for the same reason it should not be very expensive (35$ is expensive for something that will be put on the background, even if it's high quality )
don't be sad, you need more patience :], many people have less then 1% of their uploaded models sold
the advice that I can give you is to "never ever" give up making nice things , sales will come sooner or later
for textures you can include them in a separate zip file