Need help with lease in PA


We just found out that we own some mineral rights, along with another party in SouthWestern PA.. My wife’s dad has a deed going back to the 60’s that gave him ½ ownership of the mineral rights. We received a lease & offer letter in the mail for the O&G rights. Its not a lot of acres & we don’t know the other party so we’re undecided about hiring an attorney. The fees would most likely work out to be a significant % of the lease. So I have a few questions before deciding what to do.
-Is it typical for the bonus money to be stated in the separate offer letter but not in the actual lease?
-Is there a way find out what is a usual & fair offer for the bonus in the area? We don't live local to where the O& G rights are.
-It appears that there is not a max limit set on the shut-in period. & the shut-in only pays $5/ac/yr. I know that we should ask for a time limit, what is typical- months, years? Is $5/ac reasonable? It seems low.
-Any other clauses, statements to watch out for that would lead us to needing additional professional advice/help?

I would appreciate any advice. Thanks in advance for you help.