Hi, all you cycling veterans.
This millenial is in need of your experience.

I would like to create a sub-compact double, while keeping my road bike's original, 130bcd crank arms by using a Willow Triplizer.
I'm attempting to personalize the gear ratio and preserve my bike's original 80's sexiness by using the Triplizer.

I have a 1986 Centurion Ironman, with a 52x42 crankset and a 113mm bottom bracket.
I would like to get rid of the 52T chainring (outer ring) ((maybe replace it with a chain guard)); replace the 42T chainring (middle ring) with a 46T Triplizer; and attach a 30T chainring to the Triplizer.
I would like to recenter the chainline between the 46T Triplizer ('the new middle chainring') and the 30T chainring that attaches to the Triplizer.

I've read on here that by switching an 80's Ironman 113mm bb to a bb with a 5mm longer spindle typically allows one to switch from a double crank to a triple.
If this is the case, would a 118mm bottom bracket possibly suit my desired purpose? Or would a 120mm bottom bracket work instead?

I'm a known cheapskate amongst my friends on my street, which is why I'm here. I'm finally getting tired of paying people to do work on my bike that I can possibly do my self.
So, before going out and investing on a digital caliper and other tools, I wanted to post this first.
Being that I'm a cheap'azz, I'm turning into a green 'retro grouch' by default; turning others metal trash into my own golden nuggets of joy.

Any feedback would be appreciated. Even negative feedback.

Thanks

1986 Centurion Ironman