If you are on a fixed term assured shorthold tenancy until January without a break clause then there is little you can do to move early.
You can advertise for a new tenant, then introduce any interested tenants to the landlord. However, the landlord does not have to agree.
As to the windows. Has this problem been resolved or do the holes remain? The landlord should ensure the premises are safe and secure. If there is a continuing issue you can call 5he council, they will inspect. If any issues you can try to negotiate an early termination based on the council's views on safety and security of the property.
There is nothing stopping you from moving. However, the could potentially lose the deposit and under contract you will have to pay rent.
The landlord is under an obligation to mitigate loss. This means if your tenancy ends on, for example, 31 january and you vacate on 31 August, handing the keys back to the landlord/agent then technically under the contract you have to pay until 31 january BUT under the principle of mitigating loss your landlord has to take reasonable steps to relet the premises. Your landlord cannot sit back and just wait for the tenancy to expire.
See if you can get the premises inspected by the council or environmental health. If they feel it is sub standard you can you that reason to terminate the contract with refund of deposit and no future payments to pay.
Not unless it says the can break. It must specifically refer to the tenant.
Would you like me to review for you. I can review the contract as an additional service.
I have just noticed in my questions list that you have asked the question 3 times and I have responded to all three. Please accept the answer given on the other two questions then you can send me the tenancy agreement via the paperclip icon. There will then be no additional charge. generally the charge to review a document is $25 but this way it will only be $15. So it will be a discount. Hope that's fair and acceptable to you. Thanks