Oh, bummer. It sounds like she's OT. Do you think she's not feeling well? Do you see anymore teeth coming?
I agree with Ali, PD with gradual withdrawal will likely work very well for your situation. Let me see if I can't answer your questions...
I'm assuming it is easier to do this for every nap/ bedtime, rather than just bedtime when going through the initial training, so no strolling or driving to nap, if possible?
Yes, consistency and frequency are going to be the best tools you have right now. Do your method for every nap and bedtime. However, I'm a firm believer that's it's much easier to sleep train a baby that's not entirely OT, so if you get a couple short naps, I think it's worth it to APOP a nap here and there either in the stroller or car. But, at BT and NW, stick strictly to your plan.
Should I be trying to leave the room when she's quiet, or wait until she's asleep before leaving?
At this point, you'll wait until she's all the way asleep before leaving. After a few days, you can start to get closer to the door and use your voice to settle her from there. After another few days, stand at the door and do the same. Eventually, you'll be outside the door and can just go in if she needs you.
Is it ok to still let her suck my pinky, if I want to eventually wean her from this? I don't actually mind it, for now, but eventually...
To be totally honest, I wouldn't. If you eventually want to wean her from this, you might as well do it now, esp since your DH is home to support you. You don't really want to replace one prop (the breast) with another (your pinky), because ultimately that's not going to get you anywhere. If she can't settle herself to sleep at the beginning of a sleep time, she can't do it in the middle of the night either.
What do I do if she doesn't end up napping within an hour or so of trying?
Do some quiet activity, really low key and try again in an hour or so. This is also the time where if you have to APOP somewhere to get some sleep into her, I'd do it.
Should I be in the room when she is fussing, but the crying isn't escalating?
Yes, if you're doing GW, you stay there until she's asleep. Don't make eye contact and if she's fussing don't say anything, but just be a presence in the room. She gets upset when you try to leave, right? So, there's no use in playing that game.
Should I be the one who does this or will it confuse her to have DH try as well?
No, certainly DH should also play a role in the sleep training. Tracy suggested parents trade off every two nights, so that one parent isn't always doing it and always tired. Also, it will help if he's able to settle her, so you can have a break in the future. The only 'rule' with this is that the parent that starts the sleep time, finishes the sleep time. So, he can't come in and 'rescue' you, if she's not going to sleep. That will confuse her and likely lengthen the whole process.
How do I prevent OT during this phase?
It will be hard to prevent it completely, but use the APOP naps as I've described. Try to stay as close to her normal routine as possible. Do early bedtimes when daytime sleep hasn't been enough. And, since she's still nursing well at night, I'd just continue with that for now rather than fighting a bunch of OT in the MOTN. Once she gets on track during the day, you can start to work on the NF/NW. Getting her the longest nights possible will help the most with OT.
One last thing... is there a reason she's still swaddled on the bottom? If it's for warmth, you can always use a sleeping bag. Otherwise, I think it might be best to remove that, as you don't want her to get stuck in it, if she's trying to stand up, etc. But, it's your choice, if you don't think there's a safety issue in it.
Good luck, hon. You can do it!