Help!!! I'm at the end of my wits

Natural leaven is generally 20-30% (baker's %) for a standard bread (ie not panettone or a super different bread). 

am I correct in thinking that "Lievito Madre" is the Italian term for wild yeast / sourdough starter?  Is it generally maintained at 50% hydration, as referenced here: https://staffoflife.wordpress.com/natural-yeast-lievito-naturale/

If this is right, then using a higher hydration sourdough starter instead of the 50% hydration Lievito Madre in a recipe would be a matter of determining the amount of actual pre-fermented flour needed, matching that, and then adjusting the hydration in the recipe to suit. 

For example, a recipe asking for 150g Lievito Madre for 500g total flour at 70% hydration would have 100g pre-fermented flour and 50g water in the Lievito Madre, 400g flour and 300g water in the rest of the dough.  Changing it to a 100% hydration starter would mean using 200g starter (100g pre-fermented flour and 100g water), and then 400g flour and 250g water in the rest of the dough.

As for changing a recipe to use Llievito Madre instead of fresh yeast, then it would seem that you really need to determine what timing the amount of fresh yeast is supposed to generate for the amount of flour in the recipe, and then find the percentage of pre-fermented flour that will give similar timing, and then adjusting the flour / water in the final dough to accommodate the flour / water used in the pre-ferment. 

So, if your recipe includes 50g of fresh yeast (equivalent to 16.7g / 5.25 tsp of IDY) to double 1200g of flour in 6 hours at 75 degrees F (I haven't looked for a chart on what amount of yeast is used for what --- numbers for yeast are for example only and do NOT reflect actual use / timing --- you can either look for a chart or go by the recipe instructions), then you could use this post and chart (post: http://www.thefreshloaf.com/node/5381/sourdough-rise-time-table and chart here: http://www.wraithnj.com/breadpics/rise_time_table/bread_model_bwraith.htm) to determine that you would need 10% pre-fermented flour (assuming 2% salt). 

For me, I generally end up adjusting timing to suit my own schedule anyways, so would more likely follow MichaelLily's advice (since he's a professional with a great reputation) and just base my amount of starter / levain / Lievito Madre on having 10-20% pre-fermented flour in it and adjust the flour and hydration in the rest of the dough to suit.

Hopefully the charts on the rise times for pre-fermented flour are useful to you.