Tom is in home / Tom is at home

"Tom is at home" is correct. Also we can say "Tom is home".

Should be Tom is at home.
Tom is in home/ Tom is in his home are wrong.

You can say Tom is in his house

Tom is in home.

Make yourself at home. ( At home = comfortable)

In -- for a place being enclosure. e.g. in the kitchen
at -- for a place outside e.g. in the market

Tom is in his home

or

Tome is at home

兩句意思相同,都說Tom 在家裡.