Low-Zero Digbala Sun

you can try 3 mukhi rudraksha as his deity is Agni, so that will pump up the fire!

Thanks Amit.

3-mukhi for a 3 of spades haha. Is the 3-mukhi also used for worshiping the Tryambakeshwara aspect of Shiva, the form used for Pitru Dosha?

Do you know a reputable source that actually sells the real thing? Even a lot of those rudraksha and gemstone "certificates of authenticity" can be fake.

I think my own Jupiter is probably too weak for a rudraksha response in my own case though.

What I'm thinking so far is to be out in daylight as much as possible, exercise a lot during the day, and perhaps do a surya, rama, ghrini, or gayatri mantra to the Sun around noon before lunch, when the Sun is at zenith and opposite the 4th cusp.

Also, is using a stone for the Sun's position in the D1 counter-indicated if that Sun is in 0 digbala? I'm thinking it may still be ok to use because the tangible campanus cusps, the defining points of digbala, are part of a different loka than the rashi chakra and thus are not automatically connected?

If it's feasible and affordable, try to visit India and go to Tiruvannamalai temple. Probably be great for your Rahu too..
In Tamil Nadu there are "Pancha Bhoota Sthalam", which are Shiva temples associated with each of the five elements. Tiruvannamalai temple is associated with fire, and you can really feel it, in the entire town. Many a siddhar reside in the mountains there. It's among my most favourite places on earth, for its energy.
I've been there even before knowing the details of my chart etc, as my soul literally pulled me to it. I do often wonder if my Sun is way better than my chart says it is supposed to be, because experiencing the place was an automatic remedy, though such a thought was not really on my mind.