1. I've never used Hannah with Molly, Hannah probably wouldn't be a bad choice to be honest.
2. You will want all of the resser spirits to summon eventually. The amount that comes in each box of spirits is how many you will want, you wont use them all every game but there will be games where you bring out 2 shikome or 3 drowned for example. If you're beginning spirit Molly my 3 picks for spirits that are an absolute MUST are Hanged, Drowned and Onryo. The rest are all really great too and you will want them eventually.
3. As a spirit Molly player I really hate facing aggressive masters like Misaki. As far as schemes she can do most of them relatively well, though there are obvious ones like undercover breakthrough/entourage that are not really her forte.
4. This list will be fine to learn her crew with, this is very similar to my regular list. Molly can generally get by with the same base list and swap 1 or 2 models out for each game and summon models reactively to suit the game.
Tear of the Gorgon is a points sink in this list. Tear of the Gorgon is fantastic if you're using Maniacal Laugh. Generally with Molly you will use her (0) to make a spirit take an action every turn, the (0) to reactivate a model is resource intensive and will often fail if you don't have the suit in your hand, it's certainly not worth burning a stone for most of the time either. Her last (0) to gain Terrifying isn't worth 3SS over the course of the game either.
With this list I would recommend swapping Tear of the Gorgon for the Necrotic Machine and +1 SS to your cache so that you may have a full cache of 7, the extra soulstone makes a world of difference when you draw a hand full of high cards yet devoid of crows. The Necrotic Machine can inject Sybelle and give her black blood, this is great if you want to get Sybelle in to the mix and keep her safer. The necrotic machine isn't vital, but it's very useful to use his (0) to bring Philip and your Doxy forward after they've activated and done all of their card draw goodness. He's also a cheap activation.
Sybelle is great for the taxi, walking is for chumps. Being able to summon in to the enemy crew on turn 1 is huge, being able to use Sybelle to teleport Molly to safety is also really good.
Anyway, hope this helps.