4 weeks into sus and you should be feeling it by now, the dbol Im sure you are.
Adding t200 right now wont hurt anything but you should have added it at the beginning.
I did that combo last cycle. I did an amp of sust eod and 1000mg of t200 a week and it was quite a nice combo.
Im sure the effects would be more pronounced especially if from what I read in your post your only doing 250mg of sust a week.
Peace,
WCP