Is there any way I can re-use the Bitcoin Core blockchain with Bitcoin ABC wallet so that Bitcoin ABC wallet recognizes the incompatible blocks, discards them and then starts synchronizing again from August 1st? It would save me a lot of time.
Yes. Copy the Blockchain for Bitcoin over to another directory. Point Bitcoin ABC to that new directory using -datadir=[DIRECTORY] when starting up.
Next, go to Help>Debug Window>Console.
Type in this:
invalidateblock 00000000000000000019f112ec0a9982926f1258cdcc558dd7c3b7e5dc7fa148
. This will make your client discard the Bitcoin block immediately after the point of fork. If you have Bitcoin Cash peers connected to you, your client will get the Bitcoin Cash blocks from them.