thoughts on restumping exterior walls only? Feeling a bit overwhelmed on how to tackle on older home.

I'm after some advice, I own a 1880's weatherboard that has never been restumped, so it's on boulders and tree stumps, it's very low to the ground and has the original floorboards in reasonable condition. The back half of the house is added on and is on a slab. I was thinking of investing in a new roof, also the original but not causing any issues but I realised that the subsidence needs to be done first.

The house feels solid, not bouncy and level enough in most of the house except the west side which has noticeable drop. This has been the case for 20 years but it's most likely a bit worse.

I had a reblocker out to look at it who has done a lot of work in our town. As there is no access under the house we are looking at 70mm in areas, he said doing the whole house would mean 3 days of soil removal alone and would be very expensive, and pulling up the floorboards he wouldn't recommend. He said that the most important part is the structural walls not the floorboards and has given me 3 options. The west side only. The west side and the east side which is not too bad but still needs doing or the whole house.

As there is an original chimney the house can only be made level to the chimney otherwise he would raise it up much higher. I've always heard that you usually need to patch up and replaster etc but he said that that it's should be an issue, that the walls will flex. He also pointed out my other chimney in the kitchen that doesn't affect the height level is leaning out and I should consider pulling it down as it's not heritage listed as it will cost around 7k to under pin.

So I'm after advice or experiences of only doing the external walls. It will come in at around 9k for both walls but if I get them to do the whole house the cost will be 30k I'm not in the financial position to open a can of worms. I'm more after keeping the house in decent shape for possible resale in the next 2-5 years. I think the thought of the chimney a well has made me wonder if i should leave it all alone and sell sooner rather than later?