I have not filed a federal return since 2010. I just completed all of my past returns and here is what they came out to be.

2011 Owe $8,000
2012 Owe $4,428
2013 Excess $5,823
2014 Excess $5,738
2015 Excess $6088
2016 Excess $5,686
2017 Excess $8,491

Questions:
1) I am unclear of the possible penelties for the 2011,2012 that I owe taxes on. Is there a way to calculate what the total will be with taxes, interest and penelties.
2) I know that for getting old refunds you can go back only 3 years (not counting this tax year) so for me it would be 2017 (this year) and 2014,15,16 if I was entitled to any refunds....the question is with 2013...will they count that $5,823 toward the total tax bill, in other words use it as part of the offset? Understanding it can't be refunde to me, but it is still a surplus.
3) It looks to me on the refund side I have $26,003 for years 2014-2017 and potentiall another $5,823 for that 2013 year bringing the total just shy of $32,000...is the feeling that there is enough to cover any penelty, interest charges?
4) For my case, would it be a good idea to file all of the returns together? or seek a tax attorney...if so, approx would I pay an attorney to take care of this for me.

THANKS in advance