When she bites you too hard, squeal as if you're a puppy and she hurt you. Then don't pay her any attention for about a minute. Sort of give her a "time out" to let her know that she will not get to play with you if she bites you. I did this with Gemma and she knows her limits now. I wrestle her with my hand and have her chase my hand around, but she does not bite hard. She's never broken my skin or anything like that. She usually just mouths at my hand and if she gets my hand in her mouth, she stops and doesn't put any more pressure down. When she was very young, she did bite too hard sometimes so I used the squeal and ignore technique. Seems to have worked quite well!
As for the pooping, it's just about catching her in the act. You must supervise her 100% of the time that she is roaming free, and when you see that she is about to do her business in the wrong spot, stop her by making a noise or clapping your hands, take her to her pad, and tell her to go potty there. Then praise her if she finishes on the pad. The more you can catch her and correct her, the faster she is going to learn where to go.
Also, do you plan on having the pads available during the spring and summer as well? If you train her to use them now, it's going to be very confusing for her to start going exclusively outdoors all of a sudden. In my opinion, if you're going to use pads, be prepared to use them for life. I don't think you can use them when it's most convenient and then only go outdoors when the weather is nice. Gemma uses pads and she also goes potty outside during walks, but she always has a pad available inside, no matter the weather. We live in Sweden and in a second floor apartment on a busy street, so I decided pads were the best option for Gemma and me. I'm not saying that it's impossible to break the habit of using pads, but if you plan to use them on and off, it's just going to be way too confusing for her to know which days she's supposed to hold it and which days she can go whenever she pleases.
Oh, and as for the litter box training, I think you should start with that now and just skip the pads so she doesn't have to deal with the transition. It will be much harder down the road if you get her accustomed to pads. I think litter boxes are great. If doggy litter existed in Sweden, I would have liked to use a litter box with Gemma.