Shed foundation

Hi all,
Having recently built a raised garden bed, I'm now a qualified DIY'er!
I need help with my next project which is building a shed. I'm wanting to make sure I'm not making any mistakes with the way I'm building the foundation. The shed will be 5750x2850. It needs to fit in a tight spot.
The shed is sitting on waste water lines which is part of the reason I decided on using Tuff blocks for the foundation. There will be 6 Tuff blocks per bearer, spaced every 822mm.

I'm wanting the shed to sit as low as possible so we still get light into our house. So I'm planning on slotting horizontally 95x45 h4 pine straight into the tuff blocks. I'm using h4 because the clearance between the ground and timber will only be about 80mm.
There will be 3 Bearers and 12 joists in a flush frame system (again so the clearance is low) all 95x45. So the space between joists will be 522mm and the space between bearers will be 1425mm. I'm using joist hangers.
Then I think after that I'll be using structural plywood for the flooring, with a waterproof coating on top.

Is the spacing for the tuff blocks, bearers, joists, plywood all OK?

The clearance under the shed will be about 80mm because where the timber slots into the tuff blocks is 50mm from the base of Tuff block, but also I'm planning on putting down crushed gravel under the tuff blocks so the tuff blocks are positioned atleast another 30mm above the dirt. Would you be concerned about the 80mm clearance gap underneath? Is moisture likely to build up? Should I put some form of moisture barrier on the underside of the plywood?

Few things to note:
I've done drainage work under the ground, hoping it doesn't get too damp.
The load capacity of each Tuff block is 770kg.
I think I'll make the shed timber framed with colourbond walls and roof. Skillion roof with a gutter.
Yes I know it won't be an approved dwelling.
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