First of all remember this is a six month old infant who has a very rapidly growing mind; however, no ability to plan out a way to manipulate you to spoil him and deny his sibling. Please ignore the spoiling comments you've received.
You didn't mention a walker. Do they make them anymore?
I absolutely have no problem with you holding your baby as much as you can nor having him sleep with you. I mentioned to you before my perfect 7 yr. old daughter. I was just being matter of fact when saying perfect. It sounds absurd or too conceited but it really is the opinion of all of her teachers, coaches, other parents, and of course her family. She is a true angel on earth. However, she has always required a lot of attention from her first week of life she liked to be on the move. I carried her always because she communicated well that she wanted to be active and involved with whatever I was doing. Plus, she loved being in my arms or in the front carrier. As soon as I would sit down with her even if she was in my arms (unless she was breastfeeding) she would cry. So I got a lot of good exercise in those days. She hated her carseat. She hated her stroller. Sometimes she liked her bouncy seat and sometimes the swing. But what she needed most was to move around. My firstborn liked to be carried too and I did the one handed housekeeping stuff but it was easier then with a one bedroom apartment and when she started to crawl she was very content as a matter of fact she was so happy with crawling that she wasn't interested in walking. I put her in a walker at ten months. She took her first steps at 14 1/2 months. She was a bit different. She started reading at 18 months. Truly amazing but absolutely far from the perfect child.
Twelve years later with my next baby I could afford devoting a lot of attention 'cuz it was like having an only child again. But the thing about only children is they require more of your time. This time a 4 bedroom house with one handed housekeeping was more difficult plus, I was very ill (later to find out I had breast cancer). I just used instinct with raising her and one thing was different, I felt she needed a walker at 4 mos. It was an odd yet strong feeling. Now I always thought walkers weren't that good of an idea 'cuz of safety hazards but our house was a perfect set up for a baby walker. I always thought they were just a way for parents to not have to hold their babies or it could delay walking. My mother mentioned one day that she should have a walker. So at 4 1/2 months when she was pretty strong for sitting up I put her in the walker and WOW! She finally let me put her down and she was very busy on her own. I giggle when I think about how happy and independent she was. She crawled at 7 mos., walked at 12 mos. Now she is advanced in ballet and tennis.
When we have children so close together it is always a huge sacrifice in time and attention. I am sorry you have to go through that. Of course, my 12 years apart was not what I had idealized and I think only children is not an ideal either. I commend you on holding your baby, enjoy it while it lasts! Follow your instincts like you are doing with the holding and sleeping. Since sadly I chose to not have another baby because of breast cancer I can't share any experience with you on parenting the two babies together but I do know that crawling is right around the corner and a whole new experience for all of you. Have fun with each of the developmental milestones. You'll get at your wits end with one and then the next one shows up just in time.