Do you think a parent is obligated to pay college tuition, purchase books, give a monetary allowance, etc.?

My oldest stepchild will be 18 in four months. He pays child support for 2 kids, so when the oldest ages out the support order will decrease by 50%. He always pays his child support on-time (ahead of time), provides health insurance/dental, pays for their cellphone bills ($270 monthly), school expenses, & car insurance (we bought the car for the 17th b/d @ a cost of $4K cash). In addition he provides them with money to purchase their mom gifts for holidays. I recently found out that the ex-wife dictated how much money he should give each child (we agreed to provide $200 to each to spend as they saw fit). The mom was highly upset (of course they - mom and kids - expected more). The mom felt the oldest should be provided w/more than the youngest due to some behavior issues. So, he gave in and took $50 from the youngest and instructed the oldest to use it along with the $60 he had already given them for a gift for the mom. Mom wanted a g/c to an all day spa which cost $150+. The kids spent most of their money on the mom and their younger sibling (different father), b/c they said she would get mad if they hadn't. I personally think this is wrong! I told him that if he continues with this gift giving to the mom, spending all of this extra money, etc. I was filing for divorce. His response, "I feel I have an obligation to do this and I'm going to continue". So, I asked him what was he going to do when the child support decreased by %50 in a few months (because I know the mom is going to be angry). From his response I gathered that he was going to start giving the money to the child who was going to give it to the mom. Now, don't get me wrong I do believe he should help w/college expenses but not give a monetary allowance. I believe the child should use work-study and/or her part-time job for spending money. She's going to continue staying at home (she wanted to go away but the mom convinced her not to so dad could continue sending money). I have kids as well from my previous marriage (one grown and one is 16). Yes, I may help my adult child on occasion but it is not everyday, every week or every month. I even make my 16 yr old contribute $25 to his/her cell phone monthly. I want to instill independence and responsibility in my kids. Am I wrong for stating that he should do they same with his kids? I posted a previous question and was frightened by some whom had been or is my position.