4Lo blinking?

Sounds like an intermittent. That could be anything from a loose connection to a dirty switch in the 4X4 system. Probably the first thing I would try would be to find a patch of loose dirt or sand and switch it into and out of 4WD low a few times to cycle the switches and see if it cleans it up and stops the light flashing. Other than that it would require testing when the light is actually flashing to catch the problem.

Welcome to 2CarPros. That is a strange one, My guess is that the CEL was turned on by the large vacuum leak that would have set an EVAP code. Toyota likes to link systems together and when the CEL came on it would limit the 4WD so fuel cannot leak out of the "open" filler. Any change in the 4WD status or transmission will turn off the Stability Control.

The blinking check engine light means a failure that can damage the emissions system, usually it means a cylinder misfire code is stored. First thing to do would be to use a scan tool and read the codes that are turning on the lights then go from there.

That is a circuit code showing an open circuit for that solenoid. As it returned I would suspect the wiring to it as the issue. A way to test it would be to go to the connector for the transmission and check the red wire on pin 8. If you use a test light connected to battery power and touch the pin on the transmission side it should ground through the solenoid and light. Then connect the light to a ground and back probe the same wire with it connected and see if it shows power while shifting. It's somewhat common for the connector to develop problems if they get any moisture in them.

A P0420 is indicating the catalytic converter isn't working within proper range. If your scan tool can display live data you could look at both the front and rear O2 sensors and verify that by watching the rear sensors as the engine runs.
https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

This could set the lights off but it's more likely something in the ABS or traction control, which, depending on the scan tool you have it may not read those codes.
I would start with checking the converter for function then use a dealer level scan tool to see if there are any hidden codes.