Ah yes, the conversations we have here, the things we talk about!
Now. My advice here is, simplify. Lose the products that are combinations of things - like, the Peri-colace. Then you won't end up accidentally overdoing it with regard to stimulants or softeners.
Stick to one type of stimulant and one type of softener. What do you think? Would it make things more straightforward?
For the stimulant I would suggest Senokot, that is simple senna. (Drop the dulcolax, your doc is right!) Start with maybe 2 in the morning and 2 in the evening. If you stop the Dulcolax, you will need something instead as a substitute so that things don't come to a halt. Senna is much easier to taper off, so you could switch to this.
For the softener, I do agree with your doc again, Miralax. And you are a long, long, long way from overdoing it. Truly. What does it say on the bottle? I expect it says 1 to 3 a day - am I right? That's for 'normal' constipation. Long term use, 2-3 a day. You are taking 4 doses? That's ok. You could take more if you needed.
But it really is very safe. When I got blocked up and found out about it so embarrassingly at the ER, it took weeks and weeks of anything from 3 to 8 doses a day, with several days of 12 doses. Yup, 12.
Did you start the Linzess yet? And aren't I a nag?
It has just been launched here in the UK, 1st April, with the name Constella. Why on earth they can't call these things the same is beyond me. Anyway, linaclotide/Linzess/Constella - that's the stuff. Theoretically available in the UK, but if I asked my GP for it, I am sure he'd look at me blankly.
House is very quiet as husband is off on a course about narrowboat art, when he comes back he will be painting roses and castles on everything I expect.