Just saw your post as I was typing below.
It "looks" like the only damage is to the I-Beam section where the bottom die holder was welded to. That will be fairly easy for a welder to cut bottom die holder off the I-beam so the I-beam can be straighten and repaired. Then weld the bottom die holder back to I-beam, and again ADD a support below the bottom die holder so pressure from the ram is not putting a torque on the I-beam. Once the welder has the bottom die holder repaired with all the required supports, then have him go over ALL the welds to make them good welds. He might have to grind them out so the new welds can penetrate the steel. Those existing welds look like they're just "laying" on top of the steel with very little penetration. A good welder will be the person to make the call when he's looking at the press.
First and MOST important is to install a pressure gauge either in the high pressure line from pump to control valve, OR in the line from control valve to top of cylinder. Either place works, and I don't have the knowledge to say which it should be. The line from pump to control valve will give pressure both in pressing and retracting the cylinder while the line from control valve to top of cylinder will give only pressing down.
Since that ram is rated at 2500 psi a 3,000 psi gauge would be good. Here's the gauge i used: https://www.amazon.com/dp/B00FBKT9P6
Once the pressure gauge is installed you can set the max pressure on the control valve down to 2,000 psi to give a max of 20 tons. Any fittings used be sure they are rated for hydraulic service.
Good photos showing how the press is designed. Those were before the damage?
I didn't mean to run on so much, but got to typing. Remember, ONLY a good welder with knowledge of welding can really make the call.
edit: a bit more, that must have been some log splitter used to make that press. Looking at how long that I-beam is above the lower die holder I would really watch any flex in that top portion. I'm not sure I'd be comfortable with a full 25 ton, but by adjusting the control valve to a lower pressure the tons can be limited to a safe level before any flex shows.
Since the lower die bracket broke while setting the welds on a billet it's likely the pressure was only in the 10 ton range. It doesn't take much pressure to set the welds. Even my little Coal Iron 12 ton press that only put out 8 tons (Coal Iron's 12 ton press is designed to provide 9 ton) didn't use full pressure to set welds. Had I put the full 8 tons of pressure it would have mashed the billet flat. Of course the small dies my press uses will take much less pressure than the large dies used in your press.