Crank Length

[UpWrong]

A 110 BCD crankset will take a 33T ring. Might help - a bit.

[andrew_s]

(I use BOX chainset and cranks which actually go much lower than 145 ).

<googles>

Ah! Child-sized BMX cranks.

In which case, these are an affordable way of trying short cranks out.
https://www.sourcebmx.com/products/jet- ... ace-cranks
JIS square taper, 104 bcd 4-arm double (by the looks), and available in 140/150/160 for £35 for cranks only.
104 bcd allows down to 30T
or

https://www.sourcebmx.com/collections/b ... ace-cranks
JIS square taper, 110 bcd 5-arm single (I think), in 5 mm increments from 135-170 mm, £90 (or try https://scuffwheels.com/search?q=box+five)

Update:
If 150 mm is short enough, there are also these
https://www.sjscycles.co.uk/chainsets/t ... 22t-150mm/