Okay - Most important for you to keep in your mind it ---- Bigger Picture!
Look at the larger picture here - your son is 6. You can only say things to him on his level, such as - "That is great - I am so happy you are enjoying yourself with your dad."
You can also talk with your son on his level that you will not tollerate rude behavior from him - i.e. hurting your feelings, your boyfriend/fiance's feelings. And make it clear that each parent here has their special traits - ask your son to write a list of three of his fav. things about you as a mom, three things about your fiance as a parent too. Focus on this with him when he is with you and KEEP THINGS POSITIVE for your little boy.
1. This may wear off BUT
2. If it doesn't ---
a. talk to the father and tell him that he needs to try and do some quality time without the money stuff - that's crucial - use the basic idea that you are sure he'll agree as a parent in these hard ecomomic times, you do not want your son to have a false view of reality concerning having fun and money - the two do not need to be connect always.
b. another thing you can say to his father is that it would not be healthy for your son in the long run to equate "dad" with "money" and make sure you add that 'you're sure he'll agree' that he would want a better relationship than that with his son. Ask him to get creative as to keeping things simpler and making some great bonding out of that.
Bottom line M. is that you have to come from a place of "what is best for the child" with your ex -
All that said - seriously, I have been through this and the BIGGER PICTURE is that your son knows the truth - that the person he can count on and always has counted on is YOU, not his dad. Do not always focus on what he says, focus on what he doesn't say - and how he really shows who he trusts - believe me it isn't his absent father who just came out of nowhere. Be strong and know this is the truth of the matter. NEVER deviate from this truth! Hold yourself firm in this. AND later, if your ex is still in the picture and didn't get bored with the "new daddy" thing, you can bet that your son will come to you and your new husband for what he really needs - time, love, guidance, and the best of care. This is for you to know in your heart, especially if the ex doesn't comply with your wishes. Keep strong - I am a mom of three and have dealt with this twice - in the long run - the kids know who they can count on - whether they say the opposite or not.
Good luck and HAPPY THANKSGIVING!!!
Alli