Ok , you don't need to worry about a template, nor do you need a Gramp's old wonder tool.
What hes using is basically a very old pair of Tin snips. You should have something similar lying around in your tool box.
To remove the spine , you can just use a basic pair of Pliers as its not attached directly to the blade, just compression folded to grip the spine - all the rocking motion does is loosen the grip enough to let you pull out the blade.
To cut away the notch you will need metal/tin snips - nothing fancy required. Honestly, i didn't use a template either.. If you look at the razor and then put an SE blade next to it
It is very apparent which bits need to get removed, and very little metal actually needs to be taken away (plus your not snipping near the cutting edge so you don't have to be amazingly accurate.)
All your doing is widening the notch.
Besides at 50p a blade.. what the hell?!
The Autostrop is an interesting shave, Not the best Ive had certainly, but i do like shaving with the older razors.. just for the feel of history.
As for your Maybe Ever-Ready - honestly im still a bit stumped. From the looking around Ive done i still find no reference to an 'Ever-ready' brand DE.
Pal / Gem / ASR - all did DE's and they are the same company.. so i wouldn't entirely rule it out, but the search continues.
It does has a handle reminiscent to some of those made by the ASR company at the time .. but a British company named Shavex also used patterning very similar (shavex were also remiss in branding many of their razors) so its hard to tell..
Thing is the Blade wars period created a bucket load of knock offs / clones and one of a kinds.. Its almost impossible to know for sure.
Tho It may be in the 'Waits’ Safety Razor Compendium' which im hoping to get my hands on at some point.