Securing 50/50 shared residency of 5 year old boy with malicious ex

Hi,
Little advice needed on how to go about this, I'll try to keep it short.
Split 2 years ago, not been too bad between us but always random outbursts from the ex, using our child (5 years old) as a tool to get at me and my family or anyone else who upsets her. She's already made it so difficult for her own mother and step-dad to see the little guy that they have stopped contact with him, wasn't invited to her sisters wedding, her Dad has cut all ties with her, just last week has stopped my mother from having him on Wednesdays every week and has now decided to take one of my days with him away. shouting and swearing in front of him is normal for her. Just to give you an idea of the person.
So to make life more settled, 50% time spent with each of us is how I'd like it to be. I've met with my boss to discuss shift changes and reduced hours to suit. I will change jobs if I need to. At the minute he spends 3 nights a fortnight with me at weekends and i drop off and pick up from school 2 days a week. I pay her £265 a month direct into her bank, I have suggested a pattern of days with the child that suits her current work pattern but every time I ask where things are up to concerning shared residency she says that she is speaking to a solicitor, but I think this is just a delay tactic and her real concern is losing money. I have said to her there will be no payments and we should pay any academic costs, uniforms, trips, stationery, etc between us, although she will still be receiving the tax credits and such.
So really I was hoping somebody could suggest a route to take if she is not willing to come to a mutual agreement.

Many thanks,

SteR