How do I fix my crawlspace's mould problem given the floor is an improperly poured slab of concrete?
After you have done the wash, paint the floor with Drylok. In your case it would be best to use a economy grade paint sprayer given the roughness of the concrete. It will seal out the moisture (mold's happy place), and it will also keep out the bugs and plant roots in most cases. Yes, the ultimate solution would be to chip out the old floor and install a new one correctly, but if you are looking for a fix that will work nicely and not need a new back for you, go with the Drylok.