3. Can my sister and I be completely isolated from the estate's debts. All debts, the HELOC, credit cards, hospital bills, utility bills, taxes, ect.

Here is another couple of things. Depending on how it was handled that HELOC may be just another unsecured debt. If the proper paperwork was not filed then they may have no claim.

The credit cards just went poof no matter what the person on the other end says. they were in your moms name as an unsecured debt. Unless you signed to be responsible for the hospital bill..... Taxes and utility bills are tied to the house and if you have a thought about keeping it they will have to be dealt with.

As has been said you need a good person on your side.