Doing the ST in 30-35 days fully loaded is somewhat doubtful. I just did it and more in 54 days total with 43 days of actual on-the-road E to W cycling at sixty years old. Doing 100 miles a day with no days off is within human capabilities, but you must consider the fact that E to W could possibly take you straight into the teeth of W to E winds that can keep you completely off the road for days. You could miss those winds, but if you do run into that out west, you can forget about 30-35 days. You could barely move againt such winds. I hit those kinds of winds as sidewinds going from Marfa and Van Horn one year, and believe me I got off the road, got a motel room, and stopped completely. I met two guys from Germany who had been riding those winds for days, and they were extremely happy with their good luck. However, those winds disappeared the very next day after I pulled in to Van Horn.
Also, extreme weather events can set you back now and again. I have been caught out in electrical storms with winds
that brought all traffic on interstates to a complete hault. There would be no way you could move against that for hours or all day for the most part. In fact, being out in those at all in any way would be very unwise. And then there are the torrential downpours too, not exactly lethal but extremely wet and persistent.
30-35 days for the ST fully loaded and camping etc. would IMO leave too little leeway for possible / expected setbacks, and setbacks can happen. But so what. Go for it. If you are unable to do the entire route it's no big deal.
Use the maps. I assure you they will keep you off the roads you should definitely avoid.