A cleanroom process is evidence that you reimplemented without copying, but that's not enough to avoid infringing a patent. You need to redesign to avoid doing anything they claimed, convince the patent office that they made a mistake in granting some or all of the claims, hold a war chest of patents you could counter-sue with, or YOLO: https://paulgraham.com/softwarepatents.html
Yes. What I meant about valid patents is that you can’t really know what a patent is worth until you challenge it. There are SO MANY filed patents which are basically just crap, nothing more than camouflage and bluster.
