Hi,
I've attached several images which may or may not solve your problem
But let's get the easy one done first, the lower front wishbones aren't parallel to the ground but the line between the outer and inner bolts (trunnion/chassis) should be roughly horizontal.
Ok, the other stuff. The first is a copy of what Spyder used to do for their suspension reports which shows front and rear suspensions and this gives some numbers. I don't know for certain if this refers to original equipment or their modified suspension, but it will give you some idea of what they use.
The second is something I've posted before but can't find at the moment, a road test comparison between the S2 & TC (TCS should be the same) which shows dimensions for bumper height in standard form. You might be lower than this but you'll get an idea of exactly where you are against the OEM suspension.
The third is what I took from my Protech dampers in 2015 when I installed them. Initially I fitted them with the lower platform at the bottom of the damper and that looked great but not so good to drive and I raised them slightly during the first few days. They didn't bottom out on the damper stroke but the car had a lot of front/rear rake and I wanted to get it more in line with the original set-up.
I took some measurements in 2016 when I'd finally settled on the spring rates (250F, 160R) which gives you some idea of suspension movement with Protech dampers.
Finally, your ride height sounds low. My car has 195/50x15 which isn't too far away from 175/70x13 but I have 23" at the front fender. This is a bit vague and personally I'd take numbers from the chassis as a better comparison. The final image is a copy of one of my early measurements. Ignore the tracking as this was the early days and I was changing stuff around but this is the only sheet I can find which has all the ride height dimensions that I settled on in one place. (I'm lazy on completing my own forms....)
Brian
edit to add - I measure my bumper height to the point which is furthest forward/rearward on the bumper. Also my suspension is modified with 195/50x15 F, 205/50x15 R wheels.