I can't help but wonder if a lot of your worry is being driven by inaccurate weight measurements. If your pediatrician's scale was off, or your baby was weighed on different scales, or he was weighed naked one time and clothed another, that could explain why your baby's weight has seemed to pause for so long. If none of that applies, well, check out this chart: http://www.kellymom.com/babyconcerns/growth/chart2.html Your baby is very much on the chart- not below it.
As the PPs have said, all of this sounds entirely normal. Being unsettled while nursing could be due to teething, or development, or an ear infection. Having softer breasts is almost always due to the normal adjustment of milk supply to meet the baby's needs precisely, without a lot of extra left over.Around 9 moths I remember he didn't fall asleep breastfeeding anymore and sometimes would be unsettled, like he was still hungry. He'd finish quickly and even my breast wouldn't get as hard and they were softer before feeding.
You really should not blame yourself for your baby's lack of interest in solid foods. I started solids with my daughter at 6 months, and she still had zero interest in them until well into her second year. There's no window of interest that you missed.
If you're torn about weaning, then IMHO you shouldn't wean. Taking away the one thing that your baby will reliably eat isn't a sure way to get him to gain weight, accept formula or goat's milk, or eat a balanced diet of solid food.