Generally, when doing O&M training, a child is started with something that looks almost like a push walker with curved front legs. Bee transitioned from this to a white cane very early, within a month or so, but that was what her O&M instructor started with. Also, there are a LOT of different tip types for the cane, so choosing the right one is something that you generally do with O&M.
Bee has some pretty severe impulse control issues (and I can tell you being whacked in the head with a white cane HURTS) so we were adamant that the cane was not a toy. Even though she is not starting to train until September, is there any way you can speak with her instructor just to see if he/she has an objection to you getting her a cane now.
I know one family whose child was clearly not willing to wait for O&M to start walking... they got him a push wagon similar to this and padded the handle to protect his face if he fell forward. They weighed down the wagon part with bean bags and let him go. Admittedly, their walls did take a bit of a beating about 10cm off the floor 
As for the distance between you and DP. sadly, this is very common. Once the initial "shock" from friends and relatives wears off, they return to life as normal, leaving you to feel as if you are on your own - and with no one to vent to but your DP, there can be a lot of venting. I have a friend who has a child like Bee - I whinge and vent and bitch and moan to her, she does the same about her daughter to me. That way, we both have the chance to let off steam, we can both unload to someone who gets it, offer suggestions or just lend an ear, but we aren't doing it to the person who is just as stressed as we are about the same things...
We are here to talk - you can add me on FB if you like. That stress and fighting is what ends the marriages of the majority of families with complex children - recognising it now and trying to do something about it will do so much to getting through all this.