although these requirements are pretty stupid, there have been many many posts on what to input in these fields, a search would have shown you. I fear that what you have done will only delay your application.
you need to email the embassy and explain to them that you need to change the COE application to Visa Exempt. Then as said you arrange to meet the Elite people for the sticker after quaratine.
you said he cannot use it in June or July, he can use it any time. All he needs to do is apply for a COE nearer his flight date. However I take the point why apply way in advance of his flight. A month before is ample time.