Cycas revoluta is not the easiest plant to overwinter inside the house. I have several, larger ones and due to size and space requirements (they're also very prickly), overwinter mine in a big garage (from mid-December to early March). Their January temps range from 34-50, February 34-55. I may water them once over the course of the Winter. Under these conditions they do not get scale or mealy bugs, nor do their leaves yellow. Your sago pics don't look that bad. Cut off the dead leaves and try to get them out as soon as you can. I just got mine out yesterday. I get mine OUT as soon as temps stay above about 30 F as overnight lowest temps. Data that show they can tolerate down to about 15 F. is for in-the-ground (mulched) plants and I am conservative about temps when we're talking about a containerized plant (as soil temps are much colder for containers as compared to the ground).
Also, when you do put your out, place in deep shade first and gradually increase their exposure to direct sun (oherwise they will burn). I basically give these guys direct sun with some degree of protection for the hottest sun.--Mine get a bit of shading being under a strand of pruned Canadian hemlocks. Had some of these guys for over 20 years now and they are getting massive!

Appreciate your advice njoasis. I have an unheated but insulated space like your garage. Haven't used it because I worried sagos wouldn't get enough light from small windows. How much light does your garage provide please? And how soon do you fertilize after putting outside in March? Many thanks again.

The best way to destroy the scale insects is with used Coffee grounds spray. I found this trick in www.cycad.org/documents/Broome-Coffee-2007.pdf

It worked for me like a magic.