I must begin with a disclaimer: the following remarks are intended as offhand information, and should not be taken as legal advice.
The legal fees may depend on the nature and amount of the work involved, particularly on whether anything is disputed.
Traditionally, Estate lawyers used a formula based on the size of the estate, using percentages (the exact percentage declined as the Estate got bigger). Using that formula would produce a fee of about $7100. This formula has been criticized as it may result in a larger fee than the alternatives: an hourly rate, or a flat fee.
I cannot answer the rest of your questions without knowing a lot more information, but can say that it is not proper for family members to remove things without accounting for them. These decisions should be made by the executor.
How long an estate takes to be settled varies; it can be done in less time. If the house needs to be sold, that is one thing that could take some time.
Not sure what the $3,500.00 charge is for if your not using a lawyer, but based upon what is stated as involved, assuming there are not any dispute, My firm can perform the necessary work for no more than $3,500.00, plus probate costs and publication costs. If you would like to discuss the matter then please feel free to contact my office at 412-788-7560. My standard arrangement is a flat fee, not based upon a % of estate, plus $175.00 per hour if additional work is needed due to disputed claims or complex issues. You statement does not appear complex or to involve disputed claims.