There seems to be two separate issues going on here. it's hard for me to follow exacly what the issue is. It lookes like it was solved by him using mac address not ip address. Which is logical, because ip addresses will change if dhcp is on, which means when ip's change, the policy will affect a computer that it was never intended to affect. So always do mac address, even if you have dhcp turned off and assigning ip addresses statically.
The other issue with the policy and the "others". In order to successfully apply the filter, you not only have to have "others" that it will apply to, you will also have to have a policy set in place for all the other machines. If you dont, then the router won't know which "others" you are talking about. So you will have at least two policies. for example. if you have four computers 3 will have to be in it's own policy to unrestricted access, and then the other policy to have webfiltering. This is most effective.
OR, You can have all four in a policy of always allow (unrestricted) and THEN create a separate policy to deny access (or filter), using the (all others). One thing that I did not try, however, if these policies will apply to people that have manually set their IP address outside the DHCP scope.
This brings me to one feature that would be handy to some people, especially parents who's children are technically more fluent than they are, would be to have some method in place where the router will deny access to computers outside the DHCP addressing scope, without having to create numerous policies to do so.