I think the previous two Posters are absolutely correct.
Grief is a formless concept - there is no set time to 'move on' - it's just that we British love our stiff upper lips, and ideally, after about a month, any bereaved person should have ceased even thinking about their loss, perish the thought they may need to talk about it!
Is the way he behaves normal? For him - yes, and that is all he needs to feel.
It is obvious that your FIL is having problems adjusting to life alone, and needs some help.
Why not try and involve any neighbours where he lives of his own age? Is there a club or association he might consider joining? He needs to meet people who have had similar experiences, to lessen his obvious feelings of isolation.
As far as the calls go, you need to be patient - an answering machine is a good idea - but removing the need for such obsessive contact is a better one.