Hi inviktys! Thanks for the interest in modding, I'll do what I can to address your issues.
-Setting the Map Bounds does not do anything but blow up the beginning tile to the set sizeThat's actually how it's meant to be, the button's only function is to say what space the strategy map image stretches over. It's useful if the strategy map texture you plan on using has areas you didn't create terrain for.
-Clicking anywhere resets entire thing back to the one tile and the area you just clickedThat would be the game remaking the dynamic strategy map; since there actually isn't anything in a lot of the areas, the new image won't have anything there and the game feels free to scale things back down. If you want to make sure the strategy map persists at a given size, you'll have to actually set a texture image rather than rely on the automatically-generated one, or add a lot of tiles.
-How do I add tiles without having to paint all of themWe don't really have any method designed for mass-creating empty tiles and I don't really see much need to have them; the tiles will be created for you as soon as you start interacting with them anyway, setting down empties beforehand doesn't really achieve anything. However, if you really did want to do it, there may be a workaround. If you can find a blank .hgt file, you can create a ton of copies import them en-masse, using their filenames to ensure they go next to eachother. E.g. N2W2.hgt, N1W1.hgt, N2W1.hgt and N1W2.hgt will all be loaded adjacent to eachother.
That said, it's a bit of a pain, so I went ahead and rewrote the code creating the initial starting tile to get what you want instead. You can download the results here.
-When painting tiles if you exceed that 0,0 demarcation the editor crashes. why is that allowed to happen?Ah, that'd be a new bug. Thanks for reporting it, we need to set up a block on creating tiles less than 0,0. I'll try and get that in the next patch.
-When I tried painting all of them the height differences did not show up on the overlay (that blue background)There's usually a delay, it takes a bit of time for the game to have changes show up. It's a slow process to check and generate the image so we don't do it all the time. Clicking "Reset Strategy Map" will force an immediate update though.
-Are there bigger brushes than the scorpion, can I define my own size?Not by default and I don't think you can, unfortunately. Should be easy enough to add that for the next patch, though.
tldr; How I can start with all tiles loaded utilizing the full map size 0x0 210 x 215tldr; Download this.
Hope this helps!