Scorp I just had my temporary custody hearing last week. Wife was going for me having the 90 days only....not 50/50...not even an option in her mind. 'the kids need their mom more at this age' blah blah blah.
No reasoning with her, no saying we are equally qualified, she would agree that we had different strengths and weaknesses as parents, just that 'stability is really important and the kids are used to being with me during the school week'.
When she wouldn't see 50/50 as the best of a shi%*y situation I was literally on the edge for a month. When she wouldn't agree to negotiate when the judge asked her if she wanted to as a last result prior to starting the hearing and his result being final, I went from freaking out to crapping my pants.
My stbx is an awesome mother with some character defects, just like everyone. Here are some things I did that you may find helpful.
Your lawyer should know which way the person hearing your case leans based on past decisions. If he doesn't know or thinks the person leans more to giving more time to the mom, see if you can reschedule with another referee/judge that goes more with 50/50.
Go to your court house, ask the people behind the window if there are any temporary custody hearings coming up. Go to several, learn the ropes, get familiar with the environment so you are more calm when your hearing takes place. In my area they are 'open hearings' and anyone can attend. Kind of awkward but I found it immensely helpful.
Keep a journal of all your activities with the kids. If you can, go back a bit when you were together. Perhaps attend school activities like carnivals, field trips, conferences, whatever/whenever you can to show involvement in their school.
Take them around your family so that you can show a broad safety net for the kids on your side. Study up on the 'custodial factors' that the court uses when deciding custody. The couple examples I have given above fit right into those (in my area...assume pretty similar wherever you are).
Make sure you meet with your attorney several days in advance to go over likely questions, what your wife may argue, get your answers somewhat prepared and practice with the attorney. You will not be in a calm, peaceful state of mind when you are on the stand getting cross examined by your wife's lawyer. You will be better off with the practice helping to offset your nervousness.
Perhaps your attorney's opening question to you can be 'why do you feel you should have 50/50 custody?'. Prepare a brief statement/couple pages...no rule against having notes. Involve details from your journal. I used things like 'in the past 3 months I have went grocery shopping, gave the kids a bath 16 our of 30 times, read a story to my son 28 nights out of the last 80 days, made 52 meals, 61 snacks, took them to the park 8 times'....etc. Statistics can be your friend.
Just some ideas for you to mull over. Good luck sir.
me 41 w43 married 20 years BD 10/10/13 ILYBNILWY.... 4 kids, 21,18,8,6