Honestly, I think that since you were already prepared to supply a replacement, you should have done so without any strings attached. The customer certainly doesn't look like they were operating in good faith (based on your side), but at the same time, your responses seem a bit petty. If you wanted the defective foam back, you should have provided a return label immediately. If you don't care enough to get the foam back, you should leave the disposal of such at the discretion of the customer. Allowing someone to reuse something defect is both good for landfills and your goodwill - but rather than generate goodwill, it seems that you'd rather escalate the situation.
If I hadn't bought a F62 already, I'd probably hesitate to order now. If this is your response to $25 foam, what happens if something goes wrong when shipping goes out in full swing for $400-600 orders?