you have 2 2.5GB ports in the back of your deco... also you have 2 10 Gbe ports in the back with one optional for sfp+ if you connect all nodes from your main deco via cat 6 or cat 7 coming out of main deco at 10 Gbe to another deco input 10 and then output 10 GBE  to another one then you should achieve 10 Gbe speeds considering if your isp supports it... if you do the same with 2.5 ports then you should get only 2.5 Gbe back haul... also if you are using any switches that are only 1gb then this is your bottleneck... try spending some money on a 10 GBE switch. there are status lights on the switch that will also tell you how your network is configured

try netgear GS110mx switch...doesn't need sfp+ it all works of off Ethernet cable