Your SXB-360-SPYK has a 1/4" barb inlet, so 1/4" distribution tubing should be used to connect to your 1/2" or 3/4" drip tube.
There are a few sprinkler heads on the market that could be used on a planter bed that would not affect the performance of the turf sprinklers and would not overwater your drip areas. Old Toro 300 series stream rotors, MP Rotators and Rainbird rotary nozzles would work. The last two products could be easily adapted to fit on top of a 1/2" "riser" and would be a simple way to water your planter bed.
It sounds like you need a new diaphragm, what size and brand are your sprinkler valves? Unless they are super old or very large, consider fixing them. A new diaphragm should cost you $10-$15 and all you need is a screwdriver.
