I am by no means an expert on this spices but I have played with them quite a bit. My first suggestion is to put this tree in a bigger pot with a bonsai mix. (Equal parts: lava rock, turface, and pine bar fines). You are in the development stage so give it some room to grow. I grow mine in full sun and water every morning and in the hotter months in the afternoon as well (I live in South Florida). I use time release fertilizer and spray with a liquid fertilizer once a week with great results. Campeche/Logwood, when put in the right conditions, are extremely fast growers.
As for the branches breaking problem be sure to defoliate your tree before wiring. This will make it much easier to get the wire on tight. Also, take this opportunity to remove any thorns you can find. Your fingers will thank you for this. The defoliating will also help to promote back budding and the new leaflets sprout a purplish/red which is really beautiful. When bending the branches you should support the branch where it comes off the trunk. This is the weakest spot and if not supported the branch will just pop off if bent to far. Another tip would be to twist the branch in the direct you wired it to keep the wire tight against the branch which will also help. I hope this helps.
