The getting to temp is a power issue and even if your PCB is away from the plate in spots generally it will still work. I would up the power supply and use a 600 to 800 W PC power supply if it’s a 12v system. Use a SSR 100amp DC to DC I say 100amp because a lot are fakes… if you can get a genuine then 30plus amp is good. Use the SSR to feed power to the bed and not you Controller board.
If you used glass then it’s not flat. Glass either general or mirror or tempered is not flat and will react to temp and warp to a degree. Borosilicate Glass is inert to temp up to something like 400deg thus it is used for scientific equipment and it is flat.
You have to remember all metals move with heat. PCB board generally doesn’t move with heat. So PCB with Boro Glass Plate is the best chance you have. If you have to camp a glass bed to a metal plate… Boro or not… the metal plate moves pushing the glass. Certain metal and alloys move less but come at a price both in weight and cost.
With the PCB board the side with the visible wire traces is the side that has to be up… I see from factory some with the wires down this is just giving away heat. Look on ebay for Cork with the 3M high temp tape applied and cover the bottom it makes a massive difference.
If you want to go the tooling place i would consider just building Dbot outright and fixing the current one to build it.
For ABS try printing on a raft (if yo havn’t already) if you use S3D slicer there are good tweaking settings like how many layers for the raft and the speed of the first layer as well as density of the top raft layer. You can get reasonably quick ( for a raft setup) and good results from rafts.
I print ABS… well I hardly ever now days I use PETG far better and easier to print with and same strength or better… on Boro glass with glue stick. The only glue stick that works is Elmer’s Disappearing Purple Glue Stick. How I got onto Elmers is a company I support who have a few of my printers print direct on Boro glass (with no raft) using the elmers glue and they print thousands of cookie cutters a month.