Sizing, Anchoring, Shaping Tilemap?

[blueskined]

Hello:
I been playing around with tiledmap lately, some parts confusing me, I diged bit about these question in the forum, but couldn't find what I am after, or some posts I suspect is out of date. please check the image below:

I am testing this with some 32 * 32 square sprite, but automatically the time map's size become like this(the white outline), I figured it's 4096 by 4096, while my game view is only 960*640, so most of the tilednmap is out of the view.
what I am trying to do is, make the fish swim, horizontally, endlessly. the background should be a endless scroll view, the idea is, cache all the background sections( best 960* 640 size) into a queue, dynamically update the queue(peek, dequeue etc) based on the fish's position, so you can see, it's best the background's size is close to the view, easy for me to predict~ can be a little larger, but definatly not 4096!
my question is:
1: how to set the tilemap to custom size, regardless what is the texture's size?
2: how to make the tilemap's shape Rect instead of a square?
3: how can I anchor the tilemap, I wish the anchor point is left- middle.

or alternative way to achieve what I want?
sorry for the long post, appreciated for any help on that!
B

[unikronsoftware]

1. Tilemap settings > Tile Properties > size sets the "tile size"
2. Reduce the Dimensions on the same page
3. You cant do that right now. If you prefer, you could set up the same thing using the static sprite batcher (no tile painting, but you get full control over positions).