[Rythm]

Calling doesn't let him draw for free, he's already paying $5 for it. I think I'd call and reevaluate depending on what hit and how much he bet. On blank turns I'd bet if checked to and call/fold depending on how much he bet. If a flush card hit and he bet I'd be done with it unless he bet really small, in which case I'd probably call.

If checked to on a diamond turn I think I'd bet as well and then not put any more money in the pot. I think it's hard to get more than 1 street of value once the flush hits, and we obviously won't get that value when he has a worse J and a 4th diamond hits on the river. We also avoid an annoying river decision that way.