Crikey, a Macaw is quite a pet to suddenly find yourself responsible for.
The first thing you need to be aware of is that there are many normal household things that can kill birds - anything smelly such as air fresheners (any kind), febreeze, scented candles etc. can have them just keel off their perch in respiratory failure. The other thing is heated teflon - it blisters their lungs and airsacs and kills them painfully, so things like non-stick cookware and hair-straightening irons are potentially lethal.
I don't know a lot about Macaws, but they are very intelligent and need lots of mental stimulation or they can become destructive or start pulling their own feathers out. Lots of safe toys on rotation. Although they look scarily huge, Macaws are 'gentle giants' and are less likely to bite than for example a lovebird.
It's probably going to take him a while to settle in as they get very attached to their special human and it will take time and patience for him to see you or your husband in the same way. He's probably quite upset by all the upheaval.
They scream frequently, it is just part of their natural behaviour to scream so you'll have to get used to it. Inappropriate screaming (ie. all day every day) is usually due to boredom and loneliness. You need to pay him a lot of attention, it's no use getting another bird to keep him company because he is bonded to humans and won't take easily to another bird, so the attention needs to come from humans.
There are some good forums out there, but I am a bit out of touch with the parrot-forum-world at the moment so hopefully someone else will be able to recommend some good sites
ETA: I agree with Arlyn who has just reminded me about upatsix - glad to hear it's still going strong