Prep and paint water damaged brick with masonry paint - advice please

Hi.
I have a victorian terrace which had previously been painted with masonry paint. The paint has bubbled and peeled in places I assume from water ingress into the brick.





Ive been investigating and have found:
1- slate damp course was two bricks under ground level. Mortar is mostly missing and very soft/sandy for these two courses.



2- built with lime mortar (front of house lime rendered, internals walls lime rendered, assume wall mortar is) but pretty sure its been repointed with cement as its rock hard and paint will not come off it. From pre excavated ground level up.

3- misplaced lead in roof valley diverting water into wall cavity. Now corrected.

4- wall cavity is filled with insulation.

5- the rear wall has only lower half painted. I assume exposed brick soaks water and is trapped by lower masonry paint.



6- concrete floor and step of back door is butted to wall but is above damp course, with no damp course of its own that I can detect.

Ive dug down to expose damp course. I understand that this should be exposed another two courses below damp course. Still considering options to hold back ground level as can't excavate whole area to lower level. It has sewage pipes and concrete lumps for fence in it.
Im scraping off all paint that is loose. Bricks are very powdery. After light brush over, I plan to:

-- paint whole area with patio/driveway cleaner to kill algae. Scrub and jet wash wall carefully.
-- Fill surface of upper wall/unpainted brick at rear to make smoother surface before painting as bricks, whilst hard and solid they are cracked and pitted. Should I fill with exterior filler or cement?



-- Repoint missing mortar in two courses above damp course with cement. (not ideal but rest of wall has cement so think another two courses will not be any worse).
-- Once dry, treat exposed, powdery bricks (the previously painted ones) with oil based stabiliser (I gather the solvent has smaller molecules than the water based version so penetrates further)
-- Paint exposed brick with diluted masonry paint to further help key. -- Paint whole area with two coats weathersheild or sandtex. (any issue with water based paint on solvent stabiliser?)

Thats my plan of action and was just after any advice, pointers, confirmation Im doing the right thing before I invest any more time into this!
Many thanks.
Matt