1. There are a few reefs around Old Cut (your entrance at #1) to be careful about. They should generally be deep enough to not worry about scraping, but if the tide is low or the wind is out of the north you can bottom out. Stay centered between the visible reefs until you pass them.
2. South shoreline has several reefs, but they should be marked on charts fairly accurately. Stay away from the edge of the shoreline and for the most part you are just fine.
3. Pretty much the same as 2
4. Similar to the south shoreline, there are some oyster reefs and shallow areas as you get close to the marsh by St. Mary's bayou and the other bayous on the west end. Watch your draft and the wind. If you stay about 50 yards off the shoreline you are generally in 3+ feet of water and should have no problems.
5. No major issues until you get back closer to Gulf Cut where the shallow reefs and shelf is.
Boggy Cut may be an easier/better point of acces to the ditch versus Gulf Cut, but again - I don't know what the draft of your boat is. If it's a shallow draft flats type boat, won't make much of a difference either way. If it drafts more (1' or over) then just need to have updated charts showing the reefs to be sure you aren't bottoming out anywhere.
https://usa.fishermap.org/depth-map/east-matagorda-bay-texas/I don't know about east Matty, but the last couple of weekends the Christmas bay system has been muddy as hell due to the winds. Water isn't visible much until you get right up on the shoreline.