I recently went to AG and my setup is similar to yours, so in good company! My mash tun is a 28qt cooler, figured smaller batch sizes, smaller cooler (keep a thicker grain bed). Who knows. I too boil on an electric glass top (better not break!). I struggled the first time and split my wort into two pots, and I used DME about last 5-10 min to hit gravity. I believe my issue is my SS pot (5g) seems too thin and heat loss prevented a good boil on the glass top (used to work fine yrs ago on an electric coil- I took yrs off from brewing, but back now!). My gf's thick walled stock pot (4g) boils up just fine and my last batches, two, back to back, same day!, were 2 & 2.5g ending, with no DME, so AG. I split these into 4 1g and 1 .5g containers, to test different hop profiles on two different grain batch profiles. So I feel I get best of both worlds- lots of experimentation, AG, oh and will bottle 4.5g!! Yay!
Here's my concern as a new AG brewer. I built a braid in my rectangle tun, a loop- about 2.5' long, splits off a T in the tun. I use copper wire to hold the braid in shape to keep from riding the sides of the tun. Reading Palmer again, I'm thinking for efficiency in a rectangle tun to use a copper pipe setup with even spacing from walls and each pipe. Also, cooler I bought didn't have a spigot, I drilled one in but seems too high (1/2" off bottom). So along with rebuild I will put drain to come out bottom. So don't know your tun setup but read Palmer's informative lauter efficiency. I bet it will make a difference.
And, if going AG, go smaller batches. Besides tun changes, I may consider some smaller (3g) carboys.
Cheers!