Dating a Widower and Feeling so Confused....

I met a widower on a dating site. We exchanged text messages for a month before we even talked on the phone. We have now been dating for the past 6 months....a little background....his wife of 23 years passed away from cancer a little over 2 years ago after a 14 month battle. They had 3 children and undoubtedly had a beautiful relationship.
I asked him what he was looking for in a relationship and he said he was lonely and would like to meet someone with the same interests and to hopefully find a life companion.
I had read a lot of articles relating to dating someone who had lost a spouse so I was very cautious and did my best not to rush into anything because in the end I did not want to feel used and alone. I was not the aggressor when it came to any intimacy. I let him take the lead and after 3 months we had sex which was great, but then immediately everything started to change. He became distant and all communication was sparse. I have not seen him since that night. After a few weeks, with very minimal communication via text, he finally told me in a phone conversation that he was not expecting the flood of emotions and confusion he was feeling. The guilt... like he had cheated on his wife. He said he wouldn't be able to introduce me to his children (21, 19 and 17) they were not ready for their father to date, they didn't want a new mother. He said he wouldn't be able to bring me to his home because there were still so many of her things displayed.
He then wanted to know what my thoughts were. I wasn't sure what kind of assurance, if any, he was looking for. I told him I knew I would never be able, nor would I attempt, to be a replacement mother to his children. I lost my father in my early 40's and even at that age I had a very difficult time, 4 years after his death, accepting the new companion in her life....so I understood. I knew that there would always be a special place locked in his heart for his wife that he would treasure forever and I would never expect him to pack away his memories of her. I let him know I had come to adore him and I only wanted to share a piece of his life, but only if he wanted it also. He sounded like a weight had been lifted. That conversation ended with me telling him that I wasn't going to pressure him but I hoped that I would hear from him again someday. He quickly responded with OH YOU WILL. That response gave me a glimmer of hope and I kept my word.
After a couple of weeks I started receiving text messages; mostly about how everyday life was going nothing very personal but he missed me. I wished him a Happy Birthday and hoped he had a great day. After 3 days this is the text I received…
Hi, things are going OK. Work has been really busy…going to Indy again next week…otherwise it has just been the same old thing. I don’t know what to say, I thought I was ready…I guess not so much…huh. Not sure what you would like to do from here…I don’t want to hold you back and I’m obviously not ready for a serious relationship. Well anyways…gotta go…talk to you later.

I am so confused.
1. What I would like to do from here? What is he asking me do have any options or is he wanting me to make the decision?
2. Serious relationship? Sure I can move on…but you obviously wanted a connection or you wouldn’t have started texting me again. Am I an optional text of convenience for when you are feeling lonely because when I send a birthday text it takes 3 days for a response.
3. Is he ending it? Than is there any need for small talk. This is a text you don’t have to slowly go into it.
4. Talk to you later? Am I reading too much into this or is he leaving the door open for something…anything? Are you going to contact me?
Please, I am looking for some advise before I respond or how to respond. I don't want to add any stress to his life.