S.,
While I am not a coach, my husband was a coach for many years and some of his friends are also coaches, and I have been in on many, many discussions of these same issues. Between that and the fact that I'm a professional communicator, I hope I can shed some helpful light. These problems have been inherent in the world of coaching for years, but they do seem to be getting worse as society has changed its outlook and coaches are for some reason no longer perceived as "authority figures."
My own children are grown up now but they had some wonderful coaches over the years and my own policy was to give the coaches no grief at all. I saw other parents be real butts and felt very irritated just seeing it. In fact, one summer I withdrew my son from a baseball team, with apologies to the coach, because of one set of parents who were just too far over the top and I was just sick and tired of hearing them sit on the bench during practice and badmouth all the other kids on the team who were not "up to THEIR standards." (Their two daughters had actually been removed from more than one team on account of these parents. Sad for the girls and what a terrible example for the parents to set.)
First let me offer that if you want to send me a PM, I'll give you my e-mail address and help you with effective and non-confrontational wording for your answer to the father's e-mail.
Second, remind yourself that YOU are the coach, not every parent of a team member. You can't force someone to sign a code of conduct, but you can choose to disregard the words of parents who refuse to sign one and you can, if he ultimately is going to be completely non-cooperative, invoke the rules of your team as a reason to remove that child. I know you don't want to do that to the child because it's not the child's fault, but you do not have to put up with too much interference and drama from parents of team members; so if it truly gets out of hand, remember who you are and remove the problem for the team as a whole by removing the teammate the controversy is swirling around.
You don't say what kind of scheduling conflicts triggered the need to reschedule two games, but I am assuming that it is your own schedule that is causing the problem. Sometimes this cannot be helped and it's simply necessary to reschedule. But if it is the schedule of some parents who cannot be there, don't reschedule. They can make arrangements for their child to travel with another parent.
As for the t-shirts v. trophy matter, when parents say they'd rather have trophies, politely ask them if they are willing to provide the trophies via donation. Let's face it, funds are limited and participation is voluntary and optional.