As a quick test try and move the hub towards the middle of the room and do likewise with the PC in the office. Also for the WiFi boosters try and place them closer to the hub than the office. That will give you an idea of the maximum possible over WiFi.
The WiFi signal on the hub is not that good when compared to more expensive Asus/Link etc models however wired will always be better. If you really want or need near 100mbs in the office get a LAN 5e cable wired from the hub to your office. The cable length shouldn't go over 25m ideally but it will probably be fine longer.