running lean and engine damage

Those screws up front on the carb are for idle only and there effectiveness on the engine disappear after you get into the primary metering system. This point of activation can be seen as when the throttle plates open up past the slots in the carb and then a tad more.

The more it opens up past that point the less effective they become..and/ the vacuum signal to them diminishes so nothing is really draw out of the idle slots. Your lean/rich running problems seem slight.