See if https://www.verizon.com/support/residential/internet/highspeed/networking/setup/actiontec704wg/123754.htm covers that then you add a router.
Test to see if that makes it work better since the DSL modem router is now just a modem.
As to using 3 routers, no one I know supports or advises that. Now using routers as Wireless Access Points is well done and something I do. Read how by googling "How to use a router as a WAP?"
To use routers as WAPs, the first router is just a router and the other routers are WAPs.
Have searched for months and tried everything I could think of but can not get a successful set up going The only downside to my situation is the (previously Verizon) Actiontec Frontier DSL modem reboots itself 1-5 times a day. I have got with tech support and replacement modems throughout the 4 years living at this house but still no resolution. Due to the area this is my only ISP option.
I have a fairly large house with an outdoor office and since I am stuck with what I got I need to figure out the best way to configure this set up.
Routers available to use:
1x TP-Link Touch P5
2x Linksys Wireless-G (WRT54GSV7)
2x Random $10 eBay routers