1. You do not have to take precautionary steps in anticipation of his moves against you.
You do not have to budge to his pressures. you are also a owner of the property that too you have 80% share in the property.
If he is going to police, let him go, the police cannot take any action against you becasue it is basically a property dispute and there is an evidence that he also owns 20% share in the property, hence there is no chance tof you ignoring him.
If at all he is aggrieved as a senior citizen, he can very well approach the tribunal for senior citizens welfare, where he has to state the facts that he owns 20^ as well as he has to prove that he was driven out or he has no source to maintain himself, which cannot be possible because he has to tell lies and if the tribunal finds that he is lying before court, then his case will be dismissed after which he cannot knock the doors of any legal forum again.
2. You ask him to transfer his share in the proeprty by a registered sale deed and express that you are ready to pay the market rate towards this or vice versa, i.e., you can offer your share of property to him for sale at the market rate.
The gift deed will become a headache for life long,hence you may avoid such an subject in this connection.