Paypal does allow you to pay through them using credit cards. You can also register your bank checking account (I don't know if they will register a savings account). In my case, my checking account is my primary account.
So when you pay through Paypal, Paypal withdraws from your checking account.
Possible problem - Paypal uses one of my credit cards to back up my checking account in case there is not enough money in my checking account to cover the purchase.
I suggest that you call Paypal. The number is 402-935-2050 in the US. (Sorry, I don't know the US country code.)
It's worth a try - possibly they can use a savings account to back up your savings account - but I'm not sure.