Tammi, you sound like you are doing the right things. Continue to lean on others, family and friends in real life as well as on the Internet, for support and strength in the days, weeks, and months to come.
Grief and mourning are tricky. Despite all the pop psychology out there about this topic, most people react in very different and individual ways. Acceptance and closure do not always happen as the schedules dictate. You may have ups and downs for quite a while, and almost on a minute by minute basis. That's perfectly natural and acceptable.
I'm glad to see that you and your mother are not blaming yourselves for what happened. Even though there may have been 'warning signs', utimately, your dad was responsible for what happened. And yes, usually people who are determined to kill themselves are successful, at some point.
Again, I am very sorry for your loss. Please continue to come here if you need to talk . . .