Not that I have tons of experience with Sagos, but I would cut them off and if there are large size wounds, apply some fungicide to the wound. These things are so tough! If I am wrong, anyone, feel free to correct me!

NO!!! Keep the fronds dangling on the sago until you know for sure there is no vascular activity. Until these fronds are fully yellow or brown, keep them there!! The plant, if the fronds are dying, does pull nutrients from the dying fronds to use in the production of a new flush of leaves.

Now that it is warm, you can fertilize your sago with a high nitrogen fertilizer (cycads don't have the same nutritional needs as true palms), or, scatter the $$ granular fertilizer called Dynamite around the rootzone. This should help get the cycad to flush a healthy new flush of leaves by mid-July.