What items can be deducted from Tenant's deposit

Tenancy Deposits

Tenant has occupied my house for two years. Now leaving. Tenant has always paid rent on time and looked after the property however there are a few items on leaving that are in a worse condition. Can you please advise on what is reasonable for them to pay and what is my responsibility.

1) Carpet - the carpet was new two years ago. There are few small stains on it. Is this fair wear and tear or can I properly charge for the cleaning, and if so can I charge for some or all of it? The carpet has otherwise been looked after.

2) The windows do not close properly. The property is very near to the sea and sea salt has been a continual problem. The result is that the windows are stiff are require extra effort to have them closed. There is no evidence of deliberate damage.
This has historically been a problem however can I charge tenant to have someone fix these as one window in particular is not closing?

3) For the same reaons as above, the patio door does not lock.

Thank you
Jamie