That tool is for putting the bottom bracket in and out of a frame you dont need it to remove cranks. You only ever need to when changing or tightening BBs which is rarely
Crank extractor, like this http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_525685_langId_-1_categoryId_242558
or
http://www.tartybikes.co.uk/tools/icetoolz_crank_puller/c31p11518.html
or
http://www.tartybikes.co.uk/tools/cyclus_crank_puller/c31p559.html
What sort of riding do you do more street, natural? What rear brake Maggy,vee,disc? How long have you been riding? What geo do you like?
You should really consider all these things first
If you moved the bolt for the caliper nearest to the axle down abit by drilling a new hole/slot I think you could easily improve that mate. Other than that it looks pretty solid, nice one mate