Look into Bluetooth amplifiers where you leave the original radio in the dash but connect the amplifier to your speakers and control it from your phone.
There is a a few examples on line of these installations. One guy removed the guts of his OEM radio and adapted the volume control to an...
I had weak performance for a year couldn’t figure it out until I pulled a plug and looked at the spark. Was weak and yellow instead of blue and crisp. Changed the coil and big difference.
I agree those ignition issues slowly sneak up on you
Probably not necessary to comment but if the driveshaft is suspect did you check that the transmission yoke and pinion angles are equal? They should be within a degree or two of each other.