TLDR: I run a small business network and am starting to drown. What's next?

Hey guys. Since I'm the nerdiest of our small company, it's my job to keep things running around here. So far I've done a pretty decent job with a Synology DS413 and an ASUS RT-N66U. I've got a 24-port managed switch and a basic 8-port hub. All in all, I've got about 45 clients hitting the network at any given time (everything from IP phones (7) to Laptops (4) to desktops (10) to printers (6) to an IP Camera system to Chromecasts (4) and smart tvs (2), not to mention cell-phones and tablets(12-15) )

My Synology has been pretty solid for the better part of two years serving solely as a NAS. Access has been fine over the network. I've created a few user groups and permissions but nothing serious. The past few days though, I just can't even connect. I can ping it all day long but it's got long pings (200-400ms) and it's become unreliable for 6 employees.

My question are these:
>What's my next step? Should I be looking to the next step yet?
>Should I create some virtual LANS?
>I could use some VPN functionality but worry that this ASUS router is not manly enough with only a 450mbp/s throughput.
>Should I implement some static IPs throughout?
>Do I build a dedicated file server?
>Do I need a beefy router? If so, like what?
>What do others like me do?

No one in the same boat here? Thought I'd get a little something.

First of all if you have your network setup properly most packets will not traverse your router. Even the Wifi based packets should not be routed (within the same subnet) just switched. If you really have a hub you should investigate the 21 century especially since switch are CHEAP. I suspect you have a broadcast storm in play. I had one the other day when someone decided to plug a cable from one jack into another one. Typically most managed switch implement spanning tree and it would detect a loop and kill it but if you have a unmanaged switch or hub it will just flood the network with broadcast packets. You can use wireshark to watch/gather statistics on broadcast traffic. But most times you can just look at the lights and see the disaster and pull plugs one at a time to find the offending cable/interface.