If the frame tubes are 1/8" thick then you have adequate material to tap holes that are strong enough. I prefer fine threads in any given size, to coarse threads. I've demonstrated the strength of a tapped hole like this by picking up the whole front of my car with one 3/8" eye bolt, connected to my lift.
Try some Longacre toe plates to set toe-in. There is no way you can measure toe accurately with your method.
Longacre Toe Measurement Tools
I'd also recommend checking the wheelbase on both sides. If there's more than 1/8" difference, something's off. I made some 90 degree angle plates from MDF that were the same height as the tire radius, placed the angle against the tire and hooked the end of the tape measure behind the top edge of the angle. Run the tape to the front tire, with the wheel pointed straight ahead. Moving the tape measure reel slowly up and down near the center of the tire will reveal the shortest distance. If in doubt about the measurement, repeat 2-3 times to insure that the measurement is repeatable.
I used some home made turn plates, accurately marked with 20 degree lines and a digital level to measure caster. I cut a length of 1-1/2 aluminum angle to span across the front wheel, and taped the level to the angle, to measure both caster and camber. 4 degrees is usually considered to be a lot for a car with manual steering, but OK for a street car with power steering. As long as the steering effort doesn't seem excessive in a parking lot, it's not too much. A car like my Corvette has about 7 degrees.