Family Visitor Visa - Application help

Hello,

Me and my wife are currently inviting my in-laws to visit us in the UK this summer (this'll be the second time they have come to visit us) and we are stuck on a few questions.

1. Issuing Authority - They do not have this in their Bolivian passports. What shall we put?

2. Issuing Authority (Visa) - on their UK visa it states "RIO DE JANEIRO". Should we put Rio or should we put UK EMBASSY, BOLIVIA?

3. Type of Visa Issued - On the visa it states "C - FAMILY VISIT" is this correct?

4. Have you ever voluntarily elected to depart the UK? - What does this mean? They left the UK at the end of there 5 weeks stay in 2012 and it was within their 6 months visa validity. I'm assuming this applies to someone who overstayed?

4. Under "Total Monthly Income From" we want to add property and savings. So do we add the value of the property and the savings? This is a little confusing as it suggests the amount of money they make monthly from these? Which is next to nothing.

5. Family Details - Under Mother/Father, what should you put if the date of birth and location is unknown?

6. The amount of money they and we have exceeds the amount of money we would likely spend on this trip. How actuate should this figures mean? Can anyone give us a breakdown of maybe what they mean?

6.1 What is the cost to you personally of your trip in GBP(£)?
6.2 The total amount of money you have for this trip
6.3 The cost of the aeroplane, boat or train tickets
Is someone other than you paying for all or a part of your trip? The answer is "Yes".
6.4 What is the total amount in GBP(£)?

7. What if anything, should you put in additional details?

Thanks
Adam