Robin: 1 & 2 seem to read fine. But....
3. B told me that A asked B to convey his regards to me. Then I said Thanks for these or
thanks for those.
[Corrected]:
3. B told me that A asked B to convey his regards to me.
Then I said; "Thanks for those. [Those "regards". You could also say; "Thanks for that." [Thanks for the "conveyance".]
.
4. Thanks alot! Tom!
Corrected: "Thanks a lot, Tom!"