Here is what I found out…
Yesterday night and I am 100% sure of that, DHCP server was pointing to the CARP BOX2.
This morning I ran ipconfig /all and it was pointing to CARP BOX1, then I disabled and enabled network connection to renew DHCP and it was pointing to BOX2 again. After reading your post I disabled all rules except the one with LOAD BALANCER and changed it to default gateway.
I renewed connection and got routed to BOX1 DHCP server. Then I connected another PC to the network and got routed to DHCP BOX1.
I thought that your solution worked out. I went back to my PC renewed connection and got back on DHCP BOX2. I guess it was not enough for me, so I used another nic in my pc. I unplagued the cable from old nic into the new one and got DHCP BOX1 right away. Renewed connection and still DHCP BOX1, reverted rules to original ones and still DHCP BOX1. It does not matter now how many times I renew connection I still get BOX1.
For the moment I thought that it should work now. I went back to PC that I just connected to network. It was sitting on DHCP BOX1. I renewed connections and it went to DHCP BOX2.
I am guessing that this is not the firewall problem!