Owning your own home

Long post

Maybe the hivemind could provide some advice.
Me and my partner are first time buyers, offer accepted on a house. It was fresh on the market and we offered full asking price as we are very keen on it, didn't want to be outbid and just wanted to make it all quick and easy.
It's a 100 year old house. We knew full well there would be some moisture, plenty of routine maintenance. I am happy to have a go at a lot myself, all no worries.
We had a survey done anyway which showed up lots of what we expected: moisture readings in the walls, bits of repointing needed and some pointing that has been repaired with cement mortar that has cracked and needs redoing. All fine.
It also however pulled up some more serious issues, primarily with the roof:
1) Several broken, slipped, missing or loose tiles. They're the original slate tiles.
2) Lots of tiles fixed with tingles. Potentially inidicating original nails/fixtures are at end of life and failing regularly now.
3) Roof is unlined. Not a problem but given the above, water is getting in.
4) There is rot in the roof timbers due to the above and also insufficient insulation in the attic.
5) There is evidence of both woodworm and wood boring beetle in the roof timber. Not sure if current or historic infestiation.
4) Chimney stack mortar has failed in several places, the pots are uncapped despite the fireplaces being closed within the house. There is water staining on the walls of the chimney breasts within the house due to this.
5) The flashing around the chimney stack is cement and has cracked/failed in multiple places.
6) A fairly large sized zig zagging crack in the rear wall under the bedroom window. There is no lintel above the downstairs door and window which is below the crack, just brick. The owners admit the crack got worse when they had the windows replaced/double glazed. Potentially a not insignificant structural issue here requiring a steel put in. As it is, the weight of the upstairs walls could be partially supported by the downstair door and window surround. Those are original single glazed. The rest of the house has been double glazed apart from these two...(do they know the wall is fucked and have left this window and door precisely because they don't want to take on the work?)

Surveyor suggests the roof is end of life. It might last the rest of the winter but it won't do another one. You could keep having someone come out and replace the fallen tiles but eventually the cost will outweigh just having it replaced. Especially considering the timber is not in good shape.
The issues with the chimney stack are where the water is coming in which is causing damp inside the house and in the roof.
The rear wall is a big worry and if it needs structural work, this will be expensive.

We've gone back to the estate agent (our solicitor just said yep, go renegotiate with the agent) and said surveyor says it needs a new roof, the chimney fixed and the rear wall looked at and fixed. We made it clear that there were a lot of other issues flagged which we are not raising since with this age of property, we expect work and are happy to do it.

Agent spoke to me on the phone and said the sellers will be happy to negotiate but they are not going to pay for a new roof "and why should they?" (wtf?).
He says as far as they're concerned, the roof is water tight and if they were not moving, they wouldn't be replacing it so why would they pay for us to replace it.
I understand this opinion, however the surveyor (who I know is likely to tell us worst case scenario) says it needs replacing or at the least recovering with adhoc timber work. I'm inclined to trust the surveyor over the seller who wants rid.

In our opinion, we're not asking them to pay for a new roof. We're saying the house is worth less because it has a buggered roof and rear wall that we didn't know about when offering asking price.
We also can't negotiate. We don't have any more money. We need them to reduce the price by enough to cover the work which I don't consider "maintenance" (It is past that), or we will have to pull out.

So I guess I'm wondering, do we think the seller is right to not have to pay to fix it all, do we think it is worth us paying more for a structural survey on the rear wall knowing they're unlikely to cough up for the work, or when presented with quotes for repairs, might they realise that all buyers are going to want the same thing and agree to pay it?

They've got full asking out of us, they must have been prepared to accept a lower offer when they put it on the market, now they're being tight about it like it's money out of their pocket. They've made 100k on the house in 10 years.

Penny for your thoughts.