Requesting Developer account while my developer account doesn't have 100$ worth of games

Isn't having multiple steam accounts against their ToS? I suggest you register here with your developer account to get the role.

What about gifting your copies with your regular account, creating multiple giveaways over time?

You can gradually create giveaways for multiple copies. This will help you reach the limit you want (every 3 completed giveaways gives you +1 slot for that).
You can also ask someone from your friends on the SG who have a lot of slots to make a giveaway instead of you.
Remember, the presence of multiple accounts is prohibited by the rules of the SG. You will have to delete the player's account.

If you want to do this giveaway to get awareness for your game and not for the SG points you could ask a higher-level member of the community to do the giveaways for you. I can currently make 130 giveaways at a time if I want to. So try and get into contact with someone you know who uses steam gifts regularly or take a chance with someone on the site with a good track record.

Or you could try and push support more with this, though from what I understand they are generally a skeleton crew (very few people) so it will take quite a while before you get a response.

Mods are shorthanded, so when matters get complicated, it takes time to get a response. On the other hand, when having like barely 20-30 GA slots I was planning an event with 40+ GAs, my request for a temporary increase of the limit has been positively answered in a day or two (and actually those extra GA slots have never been removed from my account).

I think, that very likely the issue was, that they were just not convinced, that the 2 accounts really belong to the same person. Posting a link to your player account in profile description of your Steam dev account may solve this.

bump!