I've tried to read through but it's hard with so much information and some stuff possibly being out of date. Could anyone give any feedback if this works (I think it's what I did last year).

Currently have a promo on the Plat card for $75 credit back on $200 or more in Delta bookings. My plan...

1. Purchase a $209 refundable first class ticket. Get the $75 back. (Out of pocket $134 value $209)

2. Change the refundable ticket to what I actually plan on traveling (PSC to SNA in Oct) in F for $379. The change should mean I have an additional charge of $170 on my Plat card. That should trigger the airline credit right? (Out of pocket $0 value now $379)

$379 flight had a total out of pocket cost of $134

RETURN Flight -----------------------------------------

3. Purchase a F ticket for $149 with a $50 Delta Gift card. That should cause $99 of additional collections on my Plat card and should trigger the remaining $30 credit. (Out of pocket $69, value $149)

4. Change that F ticket to what I actually need to travel, a $379 (SNA to PSC) ticket. My change value should be $149 which means I'll be charged an extra $230 on my credit card. (Out of pocket $230, value now $379)

$379 return flight had a total out of pocket cost of $299

Credits used; $200 airline, $75 offer, $50 gift card
Out of pocket $433
Value of flights flown $758