Advocate actually does all worms (including the dreaded lungworm) and flea, except tape worm which you can use droncit. so if you need tick you need to discuss with vet (Advantix or frontline/ something with fipronil I think are options for tick, apparently the fipronil still works on tick even though fleas are getting resistant to it, but you would then be doing a spot on fortnightly alternating them which is quite hardcore). I would get them all on the same cycle for worm and fleeing as they could be re infecting eachother. Some people here use Billy no mates as a natural remedy for flea and tick but I haven't used so don't know how reliable it is, although as you seem to have a worm problem you may need to hit everything chemically to get it undercontrol first as the flea / worm infection cycle is linked.
I do tend to use tea tree to bath my dog, but then I don't bath him unless he is DISCUSTING or i'm going to clip him.