Can a personal representative threaten to kick out?

Your uncle's duty as personal representative is to collect your grandmother's assets, pay her debts and the debts of her estate, and distribute the rest according to her Will.  You write both that your grandmother left everything to your mother, your sister and you and that your uncle "owns only half the assets," which is confusing.  Regardless, if your grandmother's home must be sold to pay her debts and the debts of her estate, you, your mother and your sister must move so that your uncle, as personal representative, can sell the home.  If the three of you can pay those bills, you might want to negotiate a Family Settlement Agreement which will allow you to remain in the home.