Hello! My name is
Samm and I'm gonna do my best to answer your questions. Welcome to Magical Hogwarts by the way! =]
1. Muggle sides of the family do not need to have an EFB even if they are Rich and/or Influential. The only time you need one is if they are part of the Magical world. So if the muggle criminal father decides to open up a casino in Diagon Alley with his muggle money and his daughters magic then you would need one, but if he is just a mob boss in Muggle London and his reach does not effect the wizarding world he does not need one. Does that make sense?
2. I'm not sure what you mean by the Headmistress will give him a good talking to? =] For what?
3. Yes if you would like to you can always expand on family members, even though she is a Squib she would still be considered "Pureblood" if she comes from a pureblooded family.
4. As far as the no magic needed magical items for the Squib mother, inherited from her pureblooded witch grandmother, I believe these things will be fine within reason. We have a magical items registry for more rare and expensive items, so you will need to pay for and/or apply for some of them. Do you have specific items in mind? I can help you determine which are allowed, which are not, and which will need to go through the registry? Here is a link to the registry:
link.
5. So to make sure I'm caught up, your character is a half blooded witch which a criminal muggle father based out of London, a pureblooded squib mother, a middle class pureblood potion making grandmother, and a middle class pureblood magical item creating grandfather?
6. The magical pen would be okay but maybe unrealistic in the Harry Potter universe, they use quills, but there are such things as self inking, auto answer, and quick quotes quills (like the one Rita Skeeter uses in Book 4 to transcribe her interview with Harry).
7. I'm not sure what you mean by strong/weak points? If your talking about on the character profile "Strengths & Weaknesses" in the personality section this is asking what is your character good or bad at, what is their best traits and their worst. For example my character
@Mihaela Lupesco is resourceful, a quick thinker, and enthusiastic. These are strengths. However she is also impatient, impulsive, and argumentative, these are weaknesses. There is another section in the profile/character sheet (towards the bottom) called Magical Strengths / Magical Weaknesses and this is where you will fill out which specific classes at school your character is good/bad at.
8. The classes offered at Hogwarts are as follows: Ancient Runes, Arithmancy, Astrology, Care of Magical Creatures, Charms, Defense Against the Dark Arts, Divination, Herbology, History of Magic, Muggle Studies, Potions, and Flying. You can chose any of these to be her magical strengths and magical weaknesses. Flying is included.
9. We do sometimes thread out the flying class so that will be interesting to read about.
Let me know what else I can answer for you. =]