Not that this is a foolproof way, as it doesn't exist, but I suggest spending more than 50% of your time together out of bed. Movies, parks, chatting over dinner, spending time getting to know each other over coffee (and what each other is looking for as well as finding out about his past relationships and how involved they were for him emotionally) - I am sure people can fake enjoying somebodies company to get to the sex part for awhile, but a willingness to do non bedroom related activities at least indicate that they are interested in being your friend at the minimum, and give you an idea if they like being with YOU, not just your body.
AnnabelMore has great advice on the Love conversation I think. I don't know how many people your bf has dated (and if he's been in love with anybody other than his wife recently), but I know the first time I fell in love with somebody besides my husband, it surprised me, not because we weren't supposed to/"allowed to" fall in love with others, just because it didn't think it would happen, so we hadn't discussed it ahead of time. Luckily it was fine with my SO, but since I have seen cases where it's all AOK to date somebody until love enters the picture, it is good to suss out the situation with him and his wife earlier if you're feeling this strongly.