userInfo to use until we are marked dirty again

Beachball with huge slowdown since upgrading to Sierra and now screen flickering. Running Sierra 10.12.3 on iMac (mid 2010). Reopened in safe mode with shift key depressed. Screen is now completely unstable with constant flickering (blinks with every typed letter, movement of mouse, and even without interaction). Already attempted test in Terminal, entering the code I found in similar thread here, but no test ran - nothing after 45 minutes. Plenty of RAM (lots of green) per report, also. Below are most common Console entries in first few minutes of being turned on. How do I fix this?

Hardware Overview:

Model Name: iMac

Model Identifier: iMac11,2

Processor Name: Intel Core i3

Processor Speed: 3.2 GHz

Number of Processors: 1

Total Number of Cores: 2

L2 Cache (per Core): 256 KB

L3 Cache: 4 MB

Memory: 4 GB

Processor Interconnect Speed: 5.86 GT/s

Boot ROM Version: IM112.0057.B03

SMC Version (system): 1.64f5

Pasted here from my Console Report:

(This when opening email)

2017-03-13 16:42:30.870564 -0500 default 16:42:30.870564 -0500 Google Chrome ENCODE: Caching encoded userInfo to use until we are marked dirty again, returning encoded result <private> opts={ LSUserActivityContainsFileProviderURL = 0; LSUserActivityContainsUnsynchronizedCloudDocs = 0; UAUserActivityContainsCloudDocsKey = 0;}

2017-03-13 16:42:31.343227 -0500 default 16:42:31.343227 -0500 useractivityd PICKING: 72008513-0DB4-4FE0-B58F-87FDC747A707/<private> as the current item-to-advertise.

2017-03-13 16:37:47.043131 -0500 default 16:37:47.043131 -0500 watchdogd [watchdog_daemon] @( wd_watchdog_open) - IOIteratorNext failed (kr=0)

2017-03-13 16:37:47.044423 -0500 default 16:37:47.044423 -0500 watchdogd [watchdog_daemon] @( wd_daemon_init) - could not open connection with the kernel watchdog

2017-03-13 16:37:47.044562 -0500 default 16:37:47.044562 -0500 watchdogd [watchdog_daemon] @( main) - cannot initialize the watchdog service

2017-03-13 16:37:48.700705 -0500 default 16:37:48.700705 -0500 DuetHeuristic-BM Rescoring all 65 activities [<private>]

2017-03-13 16:37:54.806579 -0500 default 16:37:54.806579 -0500 DuetHeuristic-BM Activity <private>: Optimal Score 0.4745 at <private> (Valid Until: <private>)

2017-03-13 16:37:57.194302 -0500 default 16:37:57.194302 -0500 watchdogd [watchdog_daemon] @( wd_watchdog_open) - IOIteratorNext failed (kr=0)

2017-03-13 16:37:57.479061 -0500 default 16:37:57.479061 -0500 watchdogd [watchdog_daemon] @( wd_daemon_init) - could not open connection with the kernel watchdog

2017-03-13 16:37:57.479159 -0500 default 16:37:57.479159 -0500 watchdogd [watchdog_daemon] @( main) - cannot initialize the watchdog service

2017-03-13 16:38:00.558489 -0500 default 16:38:00.558489 -0500 UserEventAgent Completed XPC Activity: com.apple.Safari.SafeBrowsing.Update

2017-03-13 16:38:00.562929 -0500 default 16:38:00.562929 -0500 UserEventAgent Unregistered XPC Activity: com.apple.Safari.SafeBrowsing.Update

2017-03-13 16:38:07.755344 -0500 default 16:38:07.755344 -0500 watchdogd [watchdog_daemon] @( wd_watchdog_open) - IOIteratorNext failed (kr=0)

2017-03-13 16:38:07.755815 -0500 default 16:38:07.755815 -0500 watchdogd [watchdog_daemon] @( wd_daemon_init) - could not open connection with the kernel watchdog

2017-03-13 16:38:07.755918 -0500 default 16:38:07.755918 -0500 watchdogd [watchdog_daemon] @( main) - cannot initialize the watchdog service

2017-03-13 16:38:19.967824 -0500 default 16:38:19.967824 -0500 Google Chrome Helper Failed to look up the port for "com.apple.windowserver.active" (1100)

2017-03-13 16:38:21.134273 -0500 default 16:38:21.134273 -0500 watchdogd [watchdog_daemon] @( wd_watchdog_open) - IOIteratorNext failed (kr=0)

2017-03-13 16:38:21.135143 -0500 default 16:38:21.135143 -0500 watchdogd [watchdog_daemon] @( wd_daemon_init) - could not open connection with the kernel watchdog

2017-03-13 16:38:21.135243 -0500 default 16:38:21.135243 -0500 watchdogd [watchdog_daemon] @( main) - cannot initialize the watchdog service

2017-03-13 16:38:30.230073 -0500 default 16:38:30.230073 -0500 Google Chrome Helper Failed to look up the port for "com.apple.windowserver.active" (1100)

2017-03-13 16:38:32.537508 -0500 default 16:38:32.537508 -0500 watchdogd [watchdog_daemon] @( wd_watchdog_open) - IOIteratorNext failed (kr=0)

2017-03-13 16:38:32.538307 -0500 default 16:38:32.538307 -0500 watchdogd [watchdog_daemon] @( wd_daemon_init) - could not open connection with the kernel watchdog

2017-03-13 16:38:32.538413 -0500 default 16:38:32.538413 -0500 watchdogd [watchdog_daemon] @( main) - cannot initialize the watchdog service

2017-03-13 16:38:38.661918 -0500 default 16:38:38.661918 -0500 watchdogd [watchdog_daemon] @( wd_watchdog_open) - IOIteratorNext failed (kr=0)

2017-03-13 16:38:38.662865 -0500 default 16:38:38.662865 -0500 watchdogd [watchdog_daemon] @( wd_daemon_init) - could not open connection with the kernel watchdog

2017-03-13 16:38:38.662969 -0500 default 16:38:38.662969 -0500 watchdogd [watchdog_daemon] @( main) - cannot initialize the watchdog service

2017-03-13 16:38:48.819667 -0500 default 16:38:48.819667 -0500 watchdogd [watchdog_daemon] @( wd_watchdog_open) - IOIteratorNext failed (kr=0)

2017-03-13 16:38:48.820600 -0500 default 16:38:48.820600 -0500 watchdogd [watchdog_daemon] @( wd_daemon_init) - could not open connection with the kernel watchdog

2017-03-13 16:38:48.820700 -0500 default 16:38:48.820700 -0500 watchdogd [watchdog_daemon] @( main) - cannot initialize the watchdog service