Can someone advise me on my network setup?

If you are looking to use Windows server security, you do NOT want to use remote drives. They play hell with NT security. Far better to have the drives in a proper server. And any software which demands not using ADS and similar, I would question. And on a network, why use FTP? Shared drives are visible to the network, and access can be totally controlled by NT domain security. Just buy basic network switches. And it is cheaper to buy a proper HP server, and then load whatever OS you want. The machine is dedicated and optimised to server operation, there is a serious difference in performance to a workstation in server operation. Why and access point, for just 5 users it is unlikely you will need more range than a router can manage?