Ah, maybe I should tone down the difficulty then, if every level seemed tough even with every lab stone. Perhaps most players were winning with a specific strategy that I recently nerfed. I'll make a few tweaks to most levels in the next few days.
Also, great idea about deck slots, I'll plan on adding some shortly. Shouldn't be too tricky to do. I think I'll have it unlock after Level 7 so players aren't overwhelmed too fast.