– You can get by without purchasing apps. Use TextEdit for example. Otherwise accept the cost and purchase the tools you need.
– If you need to work in Windows environment, then you have to provision for one. What’s wrong with using your old Windows laptop, rather than spending extra on Parallels and a new Windows Licence? I am assuming Windows is not your main development environment… so the old laptop – reformat it, install the minimum and make it a lean-mean-windows-machine. Else get a cheap Intel Mac and BOOTCAMP.
– Should be a no brainer. Scrap what you have and re-read installation instructions and re-install.
– Everything about Oracle is a go, providing your DB is on another machine – don’t even try to install Oracle DB on a Mac. I am an Oracle developer, and I prefer Mac over Windows for development work, but my DB is not on my Mac.
– You cannot have Oracle DB installed on MacOS, you must have another machine (Linux, Windows) for your Oracle DB. Else you must connect to your clients DB to develop.
– You can use Oracle SQL Developer and JDeveloper on Mac with great success, I have no issues.
– You can use your Mac to develop Apex and functions and procedures, just have the DB elsewhere (yea that is how it goes.)
– You do not need a cleaner on a Mac, and some cleaners will mess your system. Not sure where you got this idea. You can do all cleaning yourself using terminal commands and/or UI menus of your apps, like clear browsing history, and so on.
– You did not mention Terminal in your post. I suggest you start reading about terminal commands and educate yourself to unleash the power of command line.
– Switch to Star Ratings instead of Love/Dislike. It is in the Music Settings – show star ratings. Then, after you rate your songs, you can do a Top Rated playlist, and give rules, like how many stars to include in the playlist, etc. Also you can sort by star ratings in the Songs view. Much more powerful that a binary Love/Dislike – you have 5 stars instead to rate your songs.
Power and battery life
– Funny you mention this as your main gripe. While those are great on a Mac, Mac and macOS have way bigger advantages to be happy about… like the stable (Unix) kernel, memory management, device management, iCloud, Airdrop, Continuity, Apple Music, Messages, etc. All in all, I think power and battery are last in my list, like you can always plug your Windows laptop if battery is bad, but you can’t have the other things macOS offers.