Improve custom tx error and help msg

[brentstone]

Describe your changes

Closes #3062.

Checklist before merging

• If this PR has some consensus breaking changes, I added the corresponding breaking:: labels
  • This will require 2 reviewers to approve the changes

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 72.49%. Comparing base (ef49b3d) to head (03c9cbf).

Files with missing lines	Patch %	Lines
crates/sdk/src/tx.rs	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3757      +/-   ##
==========================================
- Coverage   72.50%   72.49%   -0.01%     
==========================================
  Files         338      338              
  Lines      104190   104195       +5     
==========================================
  Hits        75541    75541              
- Misses      28649    28654       +5     

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[mergify]

Hey @brentstone, your pull request has been dequeued due to the following reason: CHECKS_FAILED.
Sorry about that, but you can requeue the PR by using @mergifyio requeue if you think this was a mistake.