Interview and I864 questions now

My husband went today for his medical in London.  He's normally the cool one but now is stressing about the going to the interview alone as I will most likely be back in the US by the time he gets one.

Questions we have -

1.  (as I will be a self employed independent contractor in my profession)  my dad had filled out the I864 and the sponsor and my mom had filed out the I864A.  Should I be the sponsor and my dad be the joint sponsor?

2.  What type of question will they ask at the interview? My husband is stressing and convinced they are going to ask him questions to trip him up some way.  He's not helped himself today by googling things and reading different forums.  He was reading one about people in the Phillipines trying to get a US visa when I got home from work. hahaha. 

3.  Can you take a cell phone to the embassy and check it in at the guard station? I remembering going to the Embassy once (can't remember what for) and I took my cell phone and had to check it at the guard station.  Wondering if that is still the process.

Thanks to anyone who can shed some light on these things for us and share their experiences

I can't help with the visa/interview specific questions as I've only ever applied for student and visitor visas for the US, but I can help with the third one:

3.  Can you take a cell phone to the embassy and check it in at the guard station? I remembering going to the Embassy once (can't remember what for) and I took my cell phone and had to check it at the guard station.  Wondering if that is still the process.

No, they will not hold any cell phones for non-US citizens (apparently they will hold them in the US citizen services section, but they won't for people applying for visas).

He either needs to not bring the cell phone with him at all, or he can check it in at a local pharmacy down the road (can't remember the name of it off the top of my head) - they will hold it for him for a couple of pounds while he is in the embassy.

He also cannot take any other electrical items into the embassy with him at all - that includes mp3 players, e-book readers, electric car keys etc.

I went for a visa interview there in September and although I'd remembered to take out all my electrical items before going to the embassy, I completely forgot that my car keys are electric... so I had to leave the queue to get in the building and run down the street (in the rain) to put it in storage at the pharmacy .

My husband and I went through the US immigration process in 2010. 

1 - I can't help with this as we didn't use co-sponsors.  Sorry.

2 - They didn't try to trip us up at all.  I was there with my husband and pretty much just stood to the side and was ignored (I am the USC).  We had all our documentation organised and ready to go.  They pretty much asked for the documents, asked a few basic questions about his job field and then took all the documents away to review.  I think if I remember correctly they asked 3 or 4 questions total. 

3 - To reiterate KSand's response.  No you cannot take cell phones into this part of the embassy.  He will need to check them at one of the local places. 

1. You are the sponsor no matter what as you are his spouse so you have to fill out an I-864 even if you have not filed taxes last year (2011 or 2010) and not had any income to report. The I-864 is also used for co-sponsors (your father). If your father's income is sufficient to meet the sponsorship amounts then you do not need the I-864A for your mother.