access-list Local_LAN_Access standard permit host 0.0.0.0
Then apply the access-list to the desired group-policy :
group-policy XXXXXX attributes
split-tunnel-policy excludespecified
split-tunnel-network-list value Local_LAN_Access
This should solve your local network access issue.
Answer to second question you do not need to change the default gateway of VPN. VPN Adapter is virtual interface trafic does not route based on gateway over there. So no matter whatever the gateway you have does not impact on any traffic flow.
Thanks
Ajay