You need two witnesses, not a notary. You only need a notary if you wish to make the will "self-proving". In such a case, the witnesses will need to sign additionally in front of the notary. This provides an extra level of insurance in case the witnesses are not available to testify in the event of a will contest.
Document parenting time, including what you're doing to facilitate it and all of the times when he's not showing up. Generally, if a parent is missing his or her time that's their loss. The best thing you can do is protect yourself in case he tries to make a claim that you're denying him access.
Technically, if the divorce decree reserved the issue of spousal maintenance or awarded her some and she just hasn't been collecting, then it is possible. In the former case, however, I can't imagine too many scenarios in which it would be a serious possibility.