You mention, "That does fix the problem with the screen waking continually, but now the refresh rate maxes out at 30hz." Based on your description there are two things to double-check: 1. Many LG 4K displays have one DisplayPort video input, and two separate HDMI video inputs. If yours is such a display, does switching to the 'other' HDMI video input help with the refresh rate? I ask because in my experience there are cases were not all inputs within a single display will perform at the same level. 2. Many LG displays will not drive a 4K display at 60Hz refresh unless 'HDMI ULTRA HD Deep Color' is turned on with the display's internal on-screen menu settings. This option is normally available under the 'Settings' --> 'General' section of the display's onscreen menus. You may want to review the online manual for your specific model display for more information. You do not mention which specific model LG display you are using, otherwise I would reference the manual directly 
I have an XPS 9310, connected to a Kensington SD5600T TB3 USB-C Dual 4k hybrid dock, connected via DisplayPort to two LG 4k monitors. When I put the laptop to sleep, the monitors lose signal, go into low power mode, and then immediately turn back on, report that they have no signal, go into low power mode, and so on, over and over. This happens even if I'm in the BIOS, so I'm pretty sure it isn't windows related. If I unplug the laptop from the dock, the monitors go to sleep and stay that way. Firmware on laptop is up to date. Dock doesn't seem to have any firmware updates available, monitors don't have firmware updates available. Any ideas?
XPS 13 9310, external LG monitors connected Kensington dock won't stay asleep.