My initial thoughts are to change your baby's routine to reduce the number of sleeps but to sleep for longer. My 6month old is a catnapper too and she would only sleep for 20 mins or so at a time. When she wasn't sleeping I was either feeding or occupying her as she's a bit of a velcro baby. Have you tried resettling when the baby wakes up after the first sleep cycle?

I have started being really strict with DD in enforcing a sleep routine. Its still a work in progress but already I'm noticing she is starting to get into a routine and also sleeping for longer. I am lucky that my 2 year old is at daycare 4 days a week so I have had the luxury of being able to focus on getting DD into a routine which has been time consuming.

I agree that as the baby gets older the two of them can start to occupy each other and you will be less in demand.

I know this wasn't what you asked but IMO getting #2 sorted will benefit #1 and you too.