it's a strange setup you have there.
normally ALL devices in the network should have pfsense as their gateway.
is there a good reason not todo this? i currently don't know why you have your AD as gateway? is your AD doing NAT ?
Anyways, there are solution to your current problem. But fixing the gateway on the clients is the best option, hands down.
If for whatever reason, you can't/won't change the gateway to pfsense on your LAN devices, let me know and i'll try to explain how you can try to circumvent your network issues. (clue: NAT your lan-subnet over the VPN)