I do have park days for all four parks (one each), but I want to watch all the fireworks/nighttime shows and the Starlight parade, and it just doesn't seem like a good idea to count on being able to make it out of the park and to a viewing spot in time. I don't have a park hopper ticket.
AK will likely close at 6 pm in March. The water pageant will probably be around 8:45 pm.
I’d leave AK around 3 pm, 4 at the latest & catch the BC/YC bus from AK. Get off at BC (which is the 2nd stop) & walk through the resort lobby & towards Crescent Lake, turn left on the walkway around the lake towards the Skyliner boarding/Epcot International Gate.
Ride the Skyliner to Caribbean Beach. At CBR hop over to the loop that runs from CBR to Pop/AOA. At the Pop/AOA stop hop off & then reboard back to CBR. At CBR hop over to the DHS leg.

After you get off the Skyliner at DHS walk to the bus stops & grab the GF/Poly bus. Get off at either resort & enjoy that resort’s amenities if it’s a bit early for the water pageant - both resort’s QS restaurants are good - Gasparillas at the GF & Captain Cooks at the Poly. Captain Cooks has dole whips

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Around 8:30 head down to the resort’s marina & watch the water pageant from there, there are some benches on both resort’s docks if you want a seat while you wait for the water pageant.
If I was watching from the GF boat dock I’d likely add in a walk over to the QS Gasparillas after the water pageant to watch the MK fireworks & listen to the music from the patio in front of Gasparillas depending on when the fireworks were scheduled. I’m not as familiar w/ the Poly.
After the water pageant has gone by (& you’ve watched the fireworks if you’ve opted for that) board the boat to ride back to the MK. The boat runs one way - MK - GF - Poly - MK. When the boat arrives at the MK walk over to the bus stops to take your bus back to ASMusic.

It sounds like a lovely afternoon/evening & I’ve traversed all of those routes (albeit not on the same day) as a solo female & felt safe doing so even after dark.
Also, never say never, maybe it’ll be awhile before you’re able to return, but we can’t predict the future & I hope your financial future is more abundant than seems possible ATM.