Can The Landlord Change The Way I Pay Rent?
No. Not unless both parties agree to the change (cl 26).
Your lease should specify how rent is to be paid.
Can the bond be increased?
No. Standard term cl 15 says that only one bond is payable on any one tenancy agreement.
RTA section 20 specifies that a landlord may only require or accept as bond an amount not exceeding the first 4 weeks of rent payable under the tenancy agreement.
This means that the original amount of bond cannot be increased during the tenancy.
However, if you enter into a new fixed term agreement for the same premises and the original bond is released, then you could be asked to pay a new bond at the increased amount.