I had eleven years at Cisco, mostly in Tech Support and the SG300 was never popular in-house!
But if it has semi-IOS, you may be able to configure your DHCP with something similar to this old
example I've kept around... (and pulled out the option 43 that pointed an AP to a controller).
It will reserve the low end for static IP assigned server/PCs on the wire, and assumes your ISP router
address is .254 in the scope. You should be able to do something similar with your network range.
With best regards.
ip dhcp excluded-address 22.214.171.124 126.96.36.199
ip dhcp excluded-address 188.8.131.52
ip dhcp pool ap-pool
network 184.108.40.206 255.255.0.0