My advice is to build terrain with more durable materials. The materials cost differential can be very small, even for a project like this. Scrap plasticard/high impact polystyrene, acrylic, 1/8 inch medium density fiberboard/hardboard/masonite are all pretty inexpensive. Even at full cost from a good supplier, a project like yours above can be under US$10 /GBP 8.
My local shop often has cardboard-based or white styrofoam (low density)-based terrain donated. Usually this kind of terrain is destroyed in weeks our months, while the more durable terrain lasts years (and can be repaired.) I have worked with local players to repair store terrain and we don't spend time on any of the low durability terrain (sometimes removing useful bits, often just tossing the whole thing.) Poor materials also make terrain projects harder. We used cheap plaster one time and it keep getting dinged and falling off, total disaster. One Guy who used very expensive corrugated cardboard spent a huge amount of time filling in the holes in the end and was still not so satisfied with his work (even though it was pretty good.)
Since most of the labor and love put into a terrain project is the detailing and painting, I feel much better when I use good base materials.
You have a very interesting design going though and I look forward to seeing more progress on your projects.