I would start the same team (unless Stevens is fit then he'd slot in at WB). If we play like we did first half I suspect we're likely to have more joy against the WBA defence.
I do think this is the last chance for the current system. I don't think changing it in a must-win game against a team we should beat if we play ok is particularly sensible. However, if we don't beat WBA I think it needs a tweak. We're not good enough to play 4 at the back or have the players for it at this level. We'd be horribly exposed.
I think this is a fairly logical alternative. Our greatest threat are our wingbacks so push them up and drop another defensive midfielder in to cover the back.
I'd probably try
--------------Ramsdale
--------Basham-----Egan-----Ampadu
--------------Norwood---Fleck
Baldock---------------------------Stevens
--------------------Berge
-------------McGoldrick
--------------------------McBurnie
My main worry would be that Norwood doesn't have the legs for it. So, maybe
--------------Ramsdale
--------Basham-----Egan-----Stevens
-----------Ampadu---Fleck
Baldock---------------------------Lowe
--------------------Berge
-------------McGoldrick
--------------------------McBurnie