I would definitely use 1/8" thick glass, I don't know the thickness of 'picture frame' grade glass. I prefer to use a local glass company to cut my glass because they will finish or seam the edges so they aren't sharp. If that is not an option and the 'picture frame' glass is thinner than 1/8", you can laminate two thickness of the thinner glass by bonding them together with silicone.
I would use a 1" wide piece on either short end of the tank since it will be supported on three sides.
On the middle brace, I would try a 2" wide piece first as it should be able to support the glass canopy. Be sure to check how wide you will actually need the brace by dry fitting the glass canopy you have. You will want the brace wide enough so the lids have enough support.
You will need to measure the front to back dimension of the tank to get the proper length for the braces.
Eheim Pimpette #270
Eheim Pro II 2028; Classics Series -2215, 2217, 2260, 2262; Pro 2229 Wet/Dry