most of FLR also involve cuckolding because of the nature of the relation. ofcourse you might have some suspicious about cuckolding, maybe you dont like humiliation, have angst of losing your wife to bull etc. all these are normal fears and hesitations of cuckolding. even very willing cuckold husbands also has these bad emotions at the beginning of the cuckolding. i think first ask yourself whats really disturbing for you to be a cuck. such as if you dont want humiliation so you might have a relation without it, if you are very jealous so you might talk about it with wifey to have promisses she will write every pleasure she will have from other guys in your side etc.
but at the end of the day in a FLR, you should give all power to manage your marriage to your wife and since she wants to date and make sex with other guys, you should let her do this at least try this. if you wear constantly chastity and use long term orgasm denial over you, it will help you like theraphy to keep you constantly extremely horny and hungry so you can accept lots of cuckold things much more easly