I think one of the problems is that the crank has a little lip on the outside. I have picked up some larger bolts and going to try the method on the video first and hammer second.
  
 
The bottom bolt is what came with the kit

Your bearing separator has a narrower beveled area than mine or the one RT325 is using...  looks like it might be for a smaller diameter bearing like the one in the video.  The thin "wedge" part is not big enough to get under the edge of bearing.

Here's a couple of short videos i just did out in the sun to get a good shot. Weather's been terrible lately. Crank bearing is on a 360 crank & was super tight to get out a bit then semi tight all the way. Hope videos play clear enough to show my brutality haha.



 

I see what you mean about the lip. You might have to adapt your tool a bit
I always look at it like this, it's pointless tickling an itch.
I too have used that method loads of times .
You just have to get a bit brutal
Assemble and use a bit of propane on the bearing if need be .

Just a note to do with crank pin. I see it's sitting in a bit from the left side which has be worried if its 'more' than flush on the other side. Flush is ok but anymore & it 'might' rub on the outer bearing race. there is a washer on the crank between the bearing & crank wheel so giving you a fraction more safety. If if been like it for 'ever' i'm sure it'll still be ok--just eyeball it incase. Could be a slightly shorter pin at previous replacement but unlikely. Don't panic.

I cranked the larger bolts down, and finally got it!
It was a battle,
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RT325, I am not sure what you mean by the crank pin? It seemed ok but it was a ebay special.
Well.... its half way in the case right now.  
it would be fully in but I cant find the spacer. Hopefully its ok!

Na its all good. I can see its a fraction off flush, so not sticking through. "Big end crank pin i'm talking about". Was recessed on other side in earlier pic, so just thought maybe it's sticking out this side but can see its all good. Don't panic. Is this a DT250 motor.

Good, now you have the experience you'll have a better idea next time.
Just do your self a favour if you haven't already. Get an exploded diagram of the crank and make sure the correct number of parts are going back in as it's the only certain way you know it's right.

Congratulations!

If you don't mind grinding on your new tool, widening that bevel/wedge so that it can get under the bearing will make it much easier to use on a crank bearing...  yours looks like it was designed for a smaller OD bearing.

The motor is a IT400, but going into a DT 250. Its going to be a bit of a Frankenstein.