Wait to start Flashing and radio turning off

[CrawlerHauler99]

Hello All
I have a 99 7.3 with 150k. I recently purchaced my truck and a week ago my wait to start light clicks and flashes fast. also when i use my windows my lights flicker and when i turn my radio up loud. my radio also turns completely off when i use my turn signal or use my windows. also i have my ABS light on, my over drive light is blinking ans my speedometer only works past 28mph.

My guesses are a bad sensor (for the speedo/abs/overdrive light)
and a bad case of wiring, power source for everything else.

Please give me your input as i am reallly discouraged by my new purchase!