If there's a possibility that the cars battery is worn out (ie it's the original battery or the car struggles to start) then getting a new battery might be a cheap solution to the dashboard problems, as they do go abit wild when the battery is knackered.
However, i suspect due to the rev counter sticking part-way up, that it is the actual instrument cluster that's faulty. I think sometimes one of the dry solders can fail, which i'd imagine is reasonable cheap/easy to fix, but sometimes the whole instrument cluster has to be replaced. I think some places can recondition them now, but i'm not 100% sure. A search on here will reveal alot of posts about this problem, as it is pretty well known on Stilos.
I think the Stilo is the only Fiat that uses Visteon instrument clusters - everything else i've seen has Veglia Borletti ones, which don't seem anywhere near as problem-prone.