I'm no heating engineer, but if you have over pressurised the system, then maybe you are still trying to overfill a full system. Drain down until the pressure drops to below the norm, then carefully refill. Ours runs at 1 bar.
Oak flooring can and will be expensive. Neither would I use steel nails as these will rust in time and stain the expensive boards. Starting at one side of the room ( which you could clear to make life simple), Lift 2 or 3 of the old boards. Replace with redwood Tonge and groove boards. To help preve...
