My first piece of advice for you is to get someone reliable to help you! Don't try to do/plan everything yourself! It's okay to have 2 separate parties if that's what you really want, but let me warn you that planning a big party takes a lot time and work. To make things easier on yourself, I would suggest that you have only one party in a place that is easily accessible from where the majority of your guests live. Your family knows how big a deal this is and should be ready and willing to travel to celebrate his graduation. Or, if family members are coming up for the actual ceremony, have a small gathering at a local restaraunt right after the ceremony and save the big party for another date.
Yes, it is perfectly okay to invite people who weren't invited to the actual ceremony. Everyone knows that there are only a limited amount of people one can invite to attend the graduation. Since it is an affair for your husband, you might want to ask him about particular friends that he would want to invite (in addition to the list you come up with). Take into consideration your husband's personnality, as far as how formal/informal, what food to serve, what style the party is, etc... But don't have your husband do any major things, as this is a gift from you to him.
Definitely have food and music. The cheapest option is for you and family/friends cook the food yourselves and have a buffet style set-up where the guests get in line and are served food on their plate. If you wanted something more formal, you could have it catered, but this is a more pricey option.
You could allow a space during the party for speeches. I would limit it to those close family/friends who have given the most support (ask them in advance if they would like to say something). And allow your husband a chance to thank his guests for coming and any special people who helped him get through school. You could have pictures of him from childhood through the present blown up and displayed around the room or on some type of display board.
As far as places to have it, your church hall is a great and probably inexpensive place to have it. Just make sure you're aware of any restrictions they may have (i.e. what types of music are allowed, alcholic beverages?, etc...) If you know of anyone living in an apartment building, you could ask them if they have a social hall. I know that tenants can often rent it at a discounted rate. Hope this info helps!