The patch can be repaired thus
- remove loose , brush and clean with wet brush to remove dust
- when damp ( you may need to damp again if the water is drying in quickly) fill with 4:1 sand and cement (fine sharp if you have it, or rendering sand)
- cut this back when soft so that about 8-10mm back from plane of exisiting surface . Hold a bit of wood across it so that it looks even.
-scratch this for a key with a nail or trowel
After a day fill out with 5:1 render , level oit off with your bit of wood and 'rub it up' with a piece of wood or a wooden/fibreglass float is you have one. When firm, gently rub with sponge. You'll always see it,hard to match a pattern and disguise the joint but it's better than a hole and who will notice?
The cracks look like stress cracks from points like windows. I would not worry about them too much as long as nothing is hollow .
They will tend to open again or at last be a hirline if filled with render. You could mix a bit of silver sand
pc 5-1 using SBR instead of water.
Force this into the crack , which has been cleaned out and damped down. I would also paint SBR into the crack first with a small brush and push the render onto this while it is tacky.
Smoth off as best you can.
Again, you'll see this unless you can be lucky to blend in, but you'll have to live with it.
IF anything is loose, then you'll have to hack off, deal with the crack and render.