keyboard setting interferes with all other shortcuts

Security-related part of the issue:
After going into 'system settings > keyboard > shortcuts > typing', and changing the 'compose key' setting from 'Disabled' to 'Left Control', it messes up ALL keyboard shortcuts in ALL windows. This means that I cannot terminate a command in terminal (because the only way to terminate something is to hit control+c). This is a security risk because if I need something to terminate, I can't terminate it. I also cannot lock this computer using control + alt + l.

the general issue:
I cannot use this operating system without a mouse, after doing thing change in settings. All operating systems should be usable by keyboard alone. After changing this setting, I should be able to use other keyboard shortcuts (like SUPER (dash) and alt + tab (switch windows), especially since they're not associated with the control key).

The compose key doesn't even work, with the setting 'left control'. The user SHOULD have the liberty to choose whatever key combination configuration they please (instead of being confined to the limited drop-down options). If you can't get the key combination thing to work, you should try adding an option for something like 'left control + left shift' for the compose key combination.

Also, I keep my keyboard scroll lock turned on (so my keyboard will light up), but after changing this setting it turned off, and I could not turn it back on by pressing the scroll lock button (I do this by typing "xmodmap -e 'add mod3 = Scroll_Lock'" in terminal every time I restart my computer and login, then pressing the scroll lock key on my keyboard).

information:

results from typing 'lsb_release -rd':
Description: Ubuntu 16.04.1 LTS
Release: 16.04

results from typing 'apt-cache policy unity-control-center':
unity-control-center:
  Installed: 15.04.0+16.04.20160705-0ubuntu1
  Candidate: 15.04.0+16.04.20160705-0ubuntu1
  Version table:
 *** 15.04.0+16.04.20160705-0ubuntu1 500
        500 http://us.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     15.04.0+16.04.20160413-0ubuntu1 500
        500 http://us.archive.ubuntu.com/ubuntu xenial/main amd64 Packages

results from typing 'sudo dmidecode -t 2':
# dmidecode 3.0
Getting SMBIOS data from sysfs.
SMBIOS 2.7 present.

Handle 0x0002, DMI type 2, 15 bytes
Base Board Information
 Manufacturer: Gigabyte Technology Co., Ltd.
 Product Name: 970A-UD3P
 Version: x.x
 Serial Number: To be filled by O.E.M.
 Asset Tag: To be filled by O.E.M.
 Features:
  Board is a hosting board
  Board is replaceable
 Location In Chassis: To be filled by O.E.M.
 Chassis Handle: 0x0003
 Type: Motherboard
 Contained Object Handles: 0

my processor (after typing 'lscpu'):
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 8
On-line CPU(s) list: 0-7
Thread(s) per core: 2
Core(s) per socket: 4
Socket(s): 1
NUMA node(s): 1
Vendor ID: AuthenticAMD
CPU family: 21
Model: 2
Model name: AMD FX(tm)-8320 Eight-Core Processor
Stepping: 0
CPU MHz: 1400.000
CPU max MHz: 3500.0000
CPU min MHz: 1400.0000
BogoMIPS: 7032.84
Virtualization: AMD-V
L1d cache: 16K
L1i cache: 64K
L2 cache: 2048K
L3 cache: 8192K
NUMA node0 CPU(s): 0-7
Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core perfctr_nb cpb hw_pstate vmmcall bmi1 arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: unity-control-center 15.04.0+16.04.20160705-0ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-47.68-generic 4.4.24
Uname: Linux 4.4.0-47-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: Unity
Date: Fri Nov 25 21:48:40 2016
ExecutablePath: /usr/bin/unity-control-center
InstallationDate: Installed on 2016-10-24 (33 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
ProcEnviron:
 PATH=(custom, user)
 SHELL=/bin/bash
 LANG=en_US.UTF-8
 LANGUAGE=en_US
 XDG_RUNTIME_DIR=<set>
SourcePackage: unity-control-center
UpgradeStatus: No upgrade log present (probably fresh install)