The middle support piece should not be that hard to replace... I'd recommend you take out whats left and get a new one in there.
About two years ago, there was a brand new Oceanic 55 gallon tank for sale on the quick-sale table at a local fish auction... price was $25. Had a big crack going across the back of the tank, otherwise it was perfect! Towards the end of the auction, it was still there, surprising to me. I found the owner and asked what he'd take for it... bought it for $5!
I was still giddy the next day when I went to get a replacement piece of glass for it... giddiness soon rapidily left my body! Glass is expensive! I had taken in a piece on the back glass... seems Oceanic uses 5/16" glass for their 55 gallon tanks which is a very uncommon thickness in the US. Goes from 1/4" to 3/8" and the price skyrockets! I didn't feel comfortable using the 1/4", so I opted for a piece of the 3/8" and got the tempered stuff. I had to call about 25 shops before I finally found a place that would sell it to me for under $100!!
After two attempts, they got the right size and I was off to fix the tank. That's where things really got crazy! HAve you ever tried to take apart an aquarium?? I have no idea how those things ever leak, this tank was very difficult to get apart and the back glass out!! I ended up taking off the top trim piece (breaking it along the way
) and the back glass. I had to use a razor blade to cut the silicone all the way through the seams to get it apart! After getting it all apart, you have to get ALL the old sllicone off... another big PITA! The center support was just like the one you described... I razor bladed it off the back glass as well. After all was said and done, I finally was able to re-silicone it and put it back together. I used some 2x4 boards and tie-down straps to pull it together and hold it tight until it cured. After 3 days of curing, I cleaned it up and filled with water and let sit for 3 more days... no leaks. I now have that tank in my bedroom and never had a problem.
So, the point is, it's not impossible to fix it. What I would do is empty the tank and set on flat surface. Measure the center support thickness, width and length from inside glass edge to inside glass edge. Take the measurements to a glass shop and get a new piece. Cut out old pieces and clean off all old silicone thouroughly. Get some of the real aquarium adhesive/sealant and put the new glass in. You might want to leave just a tiny gap between the two pieces of glass when you put the new one back in and fill the gap with silicone. What I found out in tearing apart the busted one is that there is a really thin layer of the silicone between the two pieces of glass anywhere on the tank where two pieces meet. Corners, supports, bottom, etc all have a very thin layer of silicone between the pieces of glass, so I would try to duplicate that.
Best of luck,
