Split a number in every way possible way within a threshold
Jelly, 11 bytes
ŒṖḌfV⁼³ʋƇḶ}

Try it online!
-1 byte thanks to Jonathan Allan
-1 more byte thanks to Jonathan Allan
How it works
ŒṖḌfV⁼³ʋƇḶ} - Main link. Takes n on the left and t on the right
ŒṖ          - All partitions of the digits of n
  Ḍ         - Convert the lists of digits to a list of numbers
          } - To t:
         Ḷ  -   Yield [0, 1, 2, ..., t-1]
        Ƈ   - Filter the partitions p, keeping those for which the following is true...
       ʋ      ...with each partition p on the left and the lowered range on the right:
   f        -   Keep the numbers in the lowered range (i.e. less than t)
    V       -   Concatenate the numbers into a single number
     ⁼³     -   Is that equal to n?