Well the convention is StdCall and the packing is … I forget what … which is not really linked to C, I suppose the Windows designers did not want to risk Caller Cleanup which could hide problems for years.
Agreed Delphi is powerful - and for those like me who preferred the interface but wanted C++, CBuilder is a great tool too. We do 90% of our development in it.
For obscure reasons I loathe the C syntax, probably because I learnt ASM before reading K&R’s White Book
Realistically a ‘language’ is an instruction set, with a load of library code bolted on.
Borland (or as they are now, CodeGear) did a good job of hiding the grunt work, without making it hard to get at. I consider your path rational, although I would have used pure Delphi.
I learned C as my first language and C++ not long after. I tried to learn Delphi and I found it frustrating in as much as it was close enough to what I knew to be able to read it, but required that I look up nearly everything to program in it. And of course, the shop I was in had (what I considered to be) some horrible programming practices, making the code that much more difficult for me. What I love about it though is it is blazingly fast to compile - much faster than C++.