I am currently also playing with my Cirrus Logic CL-GD5422 card (photo attached), and I am not sure it is able to do 1024x768 as progressive. When I initialize any SVGA modes for 1024x768 (using its "proprietary SVGA mode numbering", haven't tried VESA modes), I always get an interlaced output. (does Windows support interlaced video?)
Though on the 800x600 front, it does give me 16, 256, 64K and 16M colors as progressive. So would expect for Windows to be able to support that at least. Attached supported resolution table for Cirrus Logic from the book "Programmers Guide to the EGA, VGA and SuperVGA cards", which does confirm it should be able to reach such resolutions, and higher.
Try maybe a UniVBE mode utility, or some other DOS tool that allows testing Super VGA modes? (e.g. Pinball Illusions has a 800x600 SVGA mode it supports)
1MB of VRAM should be enough to support 800x600@64K (800*600*2=960000 bytes), and 1024x768@256 colors (1024*768=786432 bytes).