Yep a new better AC would be nice
3500btu each 1000w of lights make it round to 4000 to each 1000w so you have a little room when opening and closing the door or working inside there, dehumidifier heat and etc.
For a dehumidifier how much water you give your plants per week?
I give my plants flower + veg 100L/week
So I got a dehumidifier that can take out 15L/day, 15L x 7= 105L so I'm covered and it does the job nicely.
1ton AC helps a bit with the dehumidifying too.
get a HOT and COLD AC, already did the stupid move to get a only cold one in the past, also get an Inverter motor AC technology, 40%+ saving on energy bills.