As regards the flooding outside of your pond berm. Any chance the construction work on your pond damaged some of your drain tiles adjacent to the tiles connected to the pond?

Even if they didn't hit any tiles while digging, the traffic could have displaced some of the old clay field tiles (if that is what you have).

Can you partially drain your pond (siphon or pump) without stressing your fish this spring? That might give you some more "intel" before spending money on your fixes.

Good luck on your project!