If you have it directly on the card the color will be darker. I double checked my API card with my Hanna checker (once it came in) and it read 1.78ppm.
I'd try to match the color to Humble's pictures be it on or off the card. As in- match his on card photo and his off card photo to be sure(as you can, photos do skew the color slightly)
I'd recommend ttm. Pods won't survive copper and the dragonet won't survive the 30 days without them. It'll be expensive, but I bought a bottle per tank when I did ttm. Ideally, you'd do an observation period after ttm (with any other fish) but the odds of a mandy showing symptoms are slim to none. I'd just make sure there is ZERO equipment sharing and make sure you transfer as little water as possible between transfers. Make sure all equipment and tanks are 100% dry before reusing