Network Settings Secured

You can call your provider or You can configure your router yourself to use WPA2 if its not already set to use it. Most recent routers use it now by default.

If your accounts are getting compromised its unlikely securing your network will do much to prevent it.

Why do you think they are getting compromised? What exactly is happening?

You can protect your Apple ID with Two-Factor Authentication to make it harder to compromise:

Two-factor authentication for Apple ID - Apple Support

Two-factor authentication is an extra layer of security for your Apple ID designed to ensure that you're the only person who can access your account, even if someone knows your password.

Other services may have other ways of protecting your accounts.

IPs and DNS have no bearing on security really.

DNS or domain name server, is the computer or server used to translate text url addresses to IP addresses.

For example a DNS translates "www.google.com" to 127.217.5.174. So it can send requests to it.

Generally the DNS is provided by your ISP and is automatically used, though can use other public ones like Google's or OpenDNS etc... My configuring them directly in your Router settings, or even on your computer. But there's no security benefit to this in reality.

The IP address is just how your computer identifies to other computers on the network and is controlled by your router generally. But one IP address is no more secure than another.

If you want to make your network secure, the best option is to use WPA2 encryption for the wireless connection, and use a router with a firewall. Most modern routers have one built in.

A Firewall can be set to close down ports and deny connections to computers inside the network from outside the network.

I think you need to take your computer to be assessed by someone knowledgeable. It is very hard to understand what is occurring from your description. All I can guess is that you received some sort of scam pop up or email that you responded to and you gave remote access to your computer to the scammers.

You need to seek out expert help.

If you are the do-it-yourself type of person, you need to restore all your devices to factory settings. First back up your data. Add back your applications. I re-install for the source. To be safest, you should only use apps out of the app store. If you need more, you could list the apps you need and we could comment on the reliability of them. Restore your data.

For your mac, you could run etrecheck and malware bytes. You would post the results of etrecheck here.

as for dns settings, you could change to google's dns 8.8.8.8 and 8.8.4.4. There have been compromised dns servers. Google's should be safe.

R

I think, if all that is happening, an IT person that can see your devices in person and what you are seeing may be a better option to assess the situation and offer options.