Walk away NOW. If the issues are known ahead of purchase insurance won’t cover them. You do NOT want to have to declare subsidence on your insurance quotes - most brokers just won’t cover you. Almost everything you said is a huge red flag and there are probably more “nice surprises” to come. If you have a mortgage approved already then go and find another property.
If this is your dream house, at least get a building & contents insurance quote before you go any further. You don’t want any further surprises.
Edit: source: bought a money-pit house, thought we had subsidence, we didn’t but it was a huge hassle and a lot of stress regardless. We got a bonus moth infestation out of it, though!