No one can guarantee safety from a lightning hit(even if you consult an electrical engineer). You could be doing all this, and the lightning could hit your house instead of the tree and it was all for nothing. For piece of mind, I think you have already gone over kill with 2 arrestors and a ground rod(it helps, but once again nothing is guaranteed). I've seen power poles with a #4 copper ground wire to a ground rod, and connected to the system neutral, and STILL have the pole catch on fire. Also seen microwave towers hold up well with a crows foot type grounding system, but that was honestly because the soil was good. If you think, a couple arresters and ground rod will prevent a fire from this, ...you aren't being realistic.