The maximum you can get between you is the JSB rate for your family (2 adults, 3 children) - this is currently €402.20 pw. This applies whether you both sign on or whether your wife signs for JSB and claims for all of the family.
Savings in excess of €20k may be assessed as means against you so the total amount paid could be less
Note that if you both sign on, the money won't be divided equally.
If your wife is claiming JSB, she will get €188 plus half of the child rate (€14.90 x3). You would be paid the balance (max. €124.80 + €14.90 x 3).
FIS will stop.
If your wife receives a redundancy payment, that may disqualify her from JSB for up to 9 weeks, depending on the amount.
JSB is paid for a maximum of 9 months, at which time the claim switches to JSA, which, as you know, is means-tested. Again, the maximum rate that can be paid between you is the rate for the family (€402.20) - any means would reduce this amount.