Thank you for writing to Just Answer.
It sounds like you are proceeding with great care, and so far you are doing everything that would normally be recommended.
If you are serious about this man, I think you need to consider the possibility that marriage may not be in the future with him. At 54, he has been single a very long time, most likely lived alone and may be very set in his ways.
With only one serious relationship in his history (unless there is more to the story) it's very likely he has a fear of commitment, or enjoys his freedom enough that having a wife may seem a threat to that.
At five to six months of dating, the most common mistake made is pushing for a commitment . As women, we often want the reassurance that we aren't wasting our time with a man who has no plans to go further down the road to a committed relationship.
Are you getting to know this man on a deeper level? Have you had the kind of conversations that intimate friends have? If the answer is no, and the relationship is staying at a "have a nice dinner and chat" level...that's probably all he wants. Is he including you in his activities with his friends? If not, my guess is that you will probably stay at arm's length.
And let me be clear...there is nothing wrong with companionable friendship. But I sense from your letter that you would like this relationship to be more (as you said "trying to take things slowly").
This is a man who will move very slowly, if at all, toward a permanent relationship.
The important thing is to look deeply inside yourself and see how much time you are willing to invest in a relationship that after five months is still at the dating level. Would you be happy to stay as you are for another year or two?
Your letter didn't mention how he is feeling, so my answer is based only on what you wrote. If you are both feeling the attraction, and are both having to work on taking things slowly, then disregard the paragraph above this one and just realize that turning this relationship into something more than dating will take, most likely, much longer with this man than with one who is used to, and enjoys, having a partner.
I hope this was helpful in sorting things out. Please click ACCEPT if it was, or let me know if there is more to the story.