I believe Apple is in the process of discontinuing this line, so you may want to look elsewhere.
What you’re describing definitely sounds like a networking problem, and upgrading your router to something with 802.11ac is definitely a good idea.
Network troubleshooting can be really frustrating and laborious, but generally speaking the only real way to move forward is to start re-configuring things (replacing wireless with wired; connecting everything wired and testing; trying with a different router; trying with a different cable; etc) and seeing what works.