Hello, was tagged here from @fionasfavourites so will do what I can to help!

Firstly, welcome to the Hive side (personally, it's a lot more active in my view than Steem is/was) - it's pretty much the same as SteemPeak (if you are using Peakd.com to view things) and hive.blog is the same as steemit site as far as I'm aware (I use peakd exclusively now). However, the two projects are going in different directions now since they split.

Can someone explain these weekly occurrences?
Is this a hive thing?
Was I getting hit because I hadn't logged in?

It looks like you were powering down from March 5th on Steem. On March 20th, Hive was created which copied the current state of most accounts so you would have continued this power down on HIVE too. It looks like the full powerdown has stopped now on HIVE looking at your wallet.

You weren't getting "hit" as it would have been you that started the powerdown and if you haven't logged in until now then all the actions that were initiated would have continued until fully completed like the powerdown.

did I just double my "money"???

Effectively, yes! Awesome! Now it's up to you what to do with it! A lot who use HIVE powered down their STEEM and moved it elsewhere or over to HIVE to have more influence but totally up to you what to do with it!

Change all my witness votes
Where can I learn who to vote for now???

Using peakd, there's a witness voting page where you can see all witnesses and those running v23.0 (soon to be 24.0 as there's an upgrade happening soon), some familiar names if you were aware of them on STEEM but some are not active, some new faces. There's links to their pages but a good community to look at might be the "Hive Governance" one which has discussions from the witnesses about it all - plus you can see who is admin there which will give you an idea.

Get rid of all those posting authorites to all those apps ???

In peakd, you can do all of this and see who has what posting authority from you - check yours at the link below https://peakd.com/@wizardave/permissions (might work, just changed the url from my one)

What about rewards here?
Looks like I have 50-50 from the old days.
Is that still good?

Yeah it's still 50/50 but I've noticed that my rewards have improved and things are getting paid out in HBD again because HIVE price is above a certain amount ($0.20 I think) so think it's good personally! Everyone will have their own perspective of course!

If you wanted the full rundown - here's a blog I wrote at the time which talks about the hard fork - bear in mind, this was written about 20th March so was accurate at the time!

Hope this helps, feel free to ask me about it 😃