Sorry missed those currents before, not sure where those are in the schematic.
Voltage between R1,R3 and R5 is the same as between R6, R7 and R8. So if you know voltage at that point, you also know current through R1. Do the same for R2, add the two together and you get the total current.
If understand well, using Thevenin:
1. Take my schematic from post 1 (or from your post 18, top drawing), add a 1V source to the top (Vcc), substitute the right side with Ut24 (calculated 3/7 V = 1V x 30/(30+40) ) and Rt24 = 30||40 = 17Ohm, the left side with Ut13 (calculated 0.60V = 1V x 30/(30+20) )and Rt13 = 20||30 = 12Ohm
2. Resulting schematic = your schematic, bottom drawing in post 18
3. a. Short V3 and calculate current from V2: 0.6V / (10+12+10) = 0.0188A
b. Short V2 and calculate current from V3: (3/7V) / (10+12+10) = 0.0134A
c. Sum of both a and b = 0.0321A = total current
4. R(substitute) = 1 / 0.0321 = 31.1Ohm
Something is wrong because this is different from 28.55Ohm of your post 13