iPhone 4S stuck in dock mode and other hardware problems

I have an iPhone 4S on latest iSO 6 (not updating because not enough memory), I've only had it 1 year and 8 months and its having many problems with its hardware. The biggest issue is that after using my friends dock, it keeps periodically switching back to 'dock' mode so no sounds, no volume bars but will still ring. I have tried cleaning out the dock connector with a dry paintbrush and it worked for a few days but has gone back to dock mode again. I clean it and it works normally for a days then back to dock mode. This is a horrible cycle and so annoying! I am very careful with my phone and don't get it dirty etc. It's definetly something with the hardware, should I replace the connector?

Additionally, the + volume button is stuck and wont work/release with cleaning. The battery is horrendous, goes down very quickly and often gets 'stuck' at a certain percentage before dying completely. I am absolutely disgusted by this! Paying that much money, I would expect a product like this to last much longer! Does everyone have these issues or am I exceptionally unlucky? 😟