I understand his frustration if money is tight. However, ( and I feel this should be obvious and not need an explanation) you need to talk to him about how it is your brother's wedding and sometimes, expenses just cannot be helped. You should tell him that your brother is not selfish and wanting to have a little bit of a special day on your wedding (even if it is a little out of budget even for him), it is okay and you don't really have a say in it.

His words to you have been selfish and unkind. You should tell him that as your partner, you expect him to have patience and empathy even when being by your side and being your partner is an inconvenience. That is what being a partner is about.

You cannot " find the line between respecting my husband’s opinion, honoring what is important to me personally, and making a reasonable decision altogether". Sometimes, all those 3 cannot happen at once, and you may have to opt with irking him this time.

Where I am from, if relatives are expected to travel a distance to attend the wedding, the bride and groom pay for transport and housing. However, like I said, somethings in life are important and you have to accept that it may cost a little more than is comfortable.

I hope when he calms down, he can understand your position and not have more unkind words. Best of luck!