The changes you outlined will only affect new connections, so there is no impact on existing connections through the FWSM. However, I would recommend changing the following line as follows:
no access-list microhttp extended permit ip any any
access-list microhttp extended permit tcp any any eq 80
If you use the first line (permit ip any any), this will send all IP traffic to the HTTP inspection engine. Instead, the new line (permit tcp any any eq 80), will only send traffic that uses TCP port 80 to the inspection engine, which will prevent the FWSM from attempting to inspect non-HTTP traffic.