Disadvantages in buying two sets of air tickets

I think there is an advantage to an overnight at the airport hotel on the way to Africa. You do your time change on that first flight and that impacts you. The flights are long and nice to break them up a bit. You don't want to arrive for your safari completely spent.

I also like the idea of spending time in Europe on the way back. It makes for a nice transition back home and many of the flights tend to be red eye.

Ask Delta how far your points will take you and what the extra charges amount to. Better to put all your arrangements on one itinerary instead of piecing together flights by yourself. It may be easier to talk directly to an airline agent rather than trying to do it via a website. A stop-over for several days is often possible with a multi-destination ticket. It will complicate co-vid rules.
In general, co-vid cancellations have to come from the airline, although there can be varying circumstances and some tickets with guaranteed refunds. Again, advice directly from the booking airline should clarify what is possible.

July is still a long way over the horizon. We all hope that by then COVID will be heading for the exits, or at least dwindling to the point where it's just a minor annoyance for most of us (and current models suggest it may be headed that way) -- but there is still great uncertainty about what's ahead. A lot can happen before (and during) July.

While we've seen COVID burn across Europe and the US multiple times, Africa, as a whole, is not highly vaccinated (much of Europe is). I would not be quite so sanguine as to worry primarily about getting stuck in Amsterdam or Rome on your way back.

I have flights to Egypt booked for next October. Fully cancel-able and fully refundable, of course (for the foreseeable future, there's no way I would book any expensive flight that wasn't). I have no idea if we will go to Egypt in October, and I'm fully prepared to pull the plug on that trip. The uncertainty of the COVID situation in Africa is the primary reason.

It's great to have a positive outlook, and signs do point to better times ahead -- but we've been there before (recall say, last August-September). That was before Omicron popped up. It's really tempting right now to have high expectations, but I think it's unwise to count on that. I do think we see light at the end of the tunnel, but there could be another tunnel a hundred yards down the road after we exit this one. So I would plan any trip, but most especially one to Africa, with contingency plans in place, just in case. YMMV.

I'd suggest first using Flight Aware to check the existence and dependability of the flights in which you are interested. Last year we were sold flights that hadn't been flying for the previous 18 months, which resulted in six changes/cancelations. And I do like your idea of 24+ hours in your initial layover, as after our SIX flight cancelations, our flight was completely canceled in Chicago, [#7 change] and the next flights across the pond were the next evening.

Good luck and safe travels!

I don’t think you have jumped through all the hoops to find rewards tickets to Africa. Have you asked on flyertalk? There are all kinds of goofy ways to open up rewards tickets, things like transferring the miles to Japan Airlines and finding you can book Africa flights that way. There’s simply no way for you to figure it out alone.

You should also call the Skymiles desk and tell them what you want. They can get availability that you can’t.

I don't have points, I have miles on Delta (sky miles).

Pre-covid, I broke up our flight to Namibia, with a transit in Frankfurt, by spending 2 nights (3 days--because our flight to Joburg left in the evening) in Mainz. We were really glad we did this. We enjoyed our brief visit to Mainz, and we were a bit more rested before our 10+ hour flight to Joburg followed by a shorter hop to Namibia.

Now, again, this was pre-Covid, so you may have to add that into your risk assessment, but I think it's a great idea, in general.