I understand your concerns and your dilemia.It seems like you have given alot of thought, emotion and concerns as well as examined the pros and cons etc.....of having a child.You have to follow your heart....
Besides the clock ticking why a baby now?Only you can answer that in your heart.
Yes being a mom in her 40's is hard....especially when you have medical issues!
I have always believed at least for myself that...If I was 50/50 on a decision
or even alittle doughtful that I needn't follow through.Sometimes we have no choice and are given what we are.
That can be a blessing too.

My son is 18 and autistic.When he was 13 and I was 41 I gave birth to a baby girl.She is now soon to be 6!
I have fibromyalgia,sleep apnea,narcolepsy,arthritis,DDD,etc.....etc....
OH YES it has been difficult at times.Yet I have no regrets...only joy and feeling blessed.Just follow your heart.MC