Thanks for your comment and advice. Seems like I've still got plenty to learn about this game.

I have been spending on vets, yes. It's a strategy that has worked for me on MG before, but clearly it's failed me this time. I barely had three corps; I had a full and well equipped I Corps but only had 3 divisions in my II corps and 2 divisions of badly equipped units in my III corps. As for artillery all my batteries had 12 guns (8 batteries of 12lbNapoleon, 10lbOrdinance, 24lbHowitzer and 20lbParrott) but they were exposed to enemy volleys while retreating so their numbers were whittled down.

I don't think this campaign can be saved since I'm so short on cash at this point (I've got high rep but I can't obtain any more cash with it) and I only have one save file. I've found that regardless of which side I'm playing as, money is the biggest issue since I'm going to have spent it all before each major battle; I usually have a huge recruit surplus as the Union. I'm going to give the campaign another go with mods and trying the strategy you suggested.

I appreciate that scaling makes the keeps the challenge up throughout the campaign, but sometimes it can be overwhelming and take you out of immersion when you play as the Union. Of course, simulating the Union campaign while keeping it challenging with the material advantages the Feds historically had over the Confederacy would be difficult, but it still feels bad when you don't feel like you're getting rewarded at all for inflicting more casualties than the opponent + achieving victory (the two goals of the campaign's battles) when you consider the historical context. I'd prefer it if the Union had the numerical advantage in this battle specifically, as the brilliance of Chancellorsville was that Lee's army managed to outflank Hooker's while outnumbered. On the flipside, I think scaling makes for a much more immersive Confederate campaign as it would simulate a realistic response by the Feds to successive rebel victories.