1 The landlord can not put the rent up during the fixed term of the tenancy. However as you are presumably no longer in a fixed term he can put it up. There are no restrictions on how much. However, if you and he agreed a new rent and that you could stay until March 2017 then you effectively have a new fixed term tenancy and he can not put the rent up during that time.
2 You will not be on trouble. There is no legal definition of a dwelling. I assume you have a bed, ktichen and toilet bath/shower.
3 Yes you do have rights. A right not to be harassed, a right to quiet enjoyment and a right to live in a place where the structure and exterior are kept in repair