Take 65K, divide it by .6275 and you get $40,787.5 , that is pre tax per year. Now divide that number by 12, months in a year. That give you $3,398 a month pre tax. Depending on the plan she takes, she will either get that, which is plan 1 or less if she wants to be able to give money to her beneficiary. Like I said before, we took plan #5, which give each of us less money per month, mine was figured on an average of $58K a year and I clear after taxes $2557. Your wife is going to be closer to 3 grand than 2 a month, depending on which plan she takes. When she gets to age 62 and starts drawing her SS, between the two of them IPERS and SS she will be making more retired then what she cleared while teaching.
Your second part, she is not going to be able to retire and draw at age 55 because she will not have her rule of 88. That is their rules, your age, at least 55 years old and service time has to equal 88. They do not calculate the last 3 calendar months into a year, because she will not be teaching those that last year. Its why a lot of teachers end up with a half a year service time, so they do not end up with 35 years instead its 35.5 years. It has something to do with the their calendar does not match up equally with the school Calendar. I would guess the school year runs from September to May, while theirs runs from January to December. So she will have two choices, either teach one extra year, or teach one extra semester to get the required time in to make it to her rule of 88.