hello Geezee,
your powersupply needs a upgrade, thats for sure. Use the powersupply to power everything and ground it together Led's/Raspi/PSU (powersupply)
The way is do the calculating; Raspi uses approxmately between 800mA and 1 Amps,
Ledstrip wil use between 1,5 and almost 2 Amps for 100 Leds of 5050 type > every 100 Led's more you need 2 Amps more.
it doesn't matter how much Amps your PSU can handle, the more Amps the better and will stabilize your PSU> 5 volts stay in harmony and don't shift from too low/too high. .
The guys here and myself uses big PSU from 10AMps until 35Amps myself and everything in between.
second, i would suggest a change in the config file >> probably your CPU is not running on maximum thrust, therefor the config file has to be altered
example;
# For more options and information see
# http://rpf.io/configtxt
# Some settings may impact device functionality. See link above for details
arm_freq=1400
over_voltage=6
temp_limit=80
gpu_freq=550
core_freq=525
v3d_freq=525
force_turbo=1
max_usb_current=1
avoid_warnings=1
avoid_warnings=2
avoid_pwm_p11=1
sdram_freq=500
sdram_schmoo=0x02000020
over_voltage_sdram_p=6
over_voltage_sdram_i=4
over_voltage_sdram_c=4
disable_splash=1
# uncomment if you get no picture on HDMI for a default "safe" mode
#hdmi_safe=1
# uncomment this if your display has a black border of unused pixels visible
# and your display can output without overscan
disable_overscan=1
# uncomment the following to adjust overscan. Use positive numbers if console
# goes off screen, and negative if there is too much border
#overscan_left=16
#overscan_right=16
#overscan_top=16
#overscan_bottom=16
# uncomment to force a console size. By default it will be display's size minus
# overscan.
framebuffer_width=1920
framebuffer_height=1080
# uncomment if hdmi display is not detected and composite is being output
hdmi_force_hotplug=1
# uncomment to force a specific HDMI mode (this will force VGA)
hdmi_group=1
hdmi_mode=16
# uncomment to force a HDMI mode rather than DVI. This can make audio work in
# DMT (computer monitor) modes
#hdmi_drive=2
# uncomment to increase signal to HDMI, if you have interference, blanking, or
# no display
#config_hdmi_boost=4
# uncomment for composite PAL
#sdtv_mode=2
# Uncomment some or all of these to enable the optional hardware interfaces
#dtparam=i2c_arm=on
#dtparam=i2s=on
#dtparam=spi=on
# Uncomment this to enable the lirc-rpi module
#dtoverlay=lirc-rpi
# Additional overlays and parameters are documented /boot/overlays/README
# Enable audio (loads snd_bcm2835)
dtparam=audio=on
#gpu_mem_256=128
#gpu_mem_512=256
#gpu_mem_1024=256
#overscan_scale=1
gpu_mem=512
you can find the config file on SD card,