Hello Blackace,
welcome at Stridaforum 
I need wider handlebars anyway (due to knee – bar contact with short ones) but I’d say that, at least in the beginning, the wider bars feel LESS stable.
But also, this feeling is a matter of flavour and training.
For example my local folding dealer told me that for him it is easier to ride Strida with short bars. (He is familiar with several other brands, like Brompton, Dahon, Tern and Xootr.)
And I mean it is in fact vice – versa!
Of course you are right with the weight, you can put a bit more pressure on the front wheel.
(As long as your saddle is not adjusted too low.)
I couldn’t tell if there’s a video, but the manual is not that bad:
https://www.strida.nl/en/knowledge-base/how-do-i-replace-a-strida-folding-bike-steer/
Unfortunately not any longer since several years.
But you can see that as a kind of „service“ from Ming cycle – for some it is tricky to get rid of the grips and mount new ones. That works best with pressurized air which is mostly not available for average users.
There is no need to touch the brake cable housings – but you must replace the brake cables since the original ones are too short for wide bars.
Pardon me, but here I didn’t get your point, do you mean your SX can’t stand like that?
There is no connection to the saddle, but perhaps you’re missing that part:
http://www.koreamtb.co.kr/shop/item.php?it_id=1503020110
You mean the unfolding of the bottom tube followed by the opening of the magnet connection – well done I’d say.
Here’s another correct one;
https://www.youtube.com/watch?v=4RbP0elWy7U
Kind regards,
Chris