The only thing I would change on your setup is the broadhead. If penetration is your issue either a two blade single bevel or a smaller mechanical should do it. Swap those sevrs onto your current arrows and you should be good to go. I doubt you'll need more poundage on your bow.

If you're looking for more speed the only other thing I'd mess with is your nocks and your fletching. Smaller vanes for less drag. You shouldn't need much since you're only steering a mechanical. And nocks that'll give you a faster cleaner release.

 

Will the bow shoot a fixed blade with your field points? If it doesn’t, your mechanical broadhead is just wasting energy too.

 

I've never shot a fixed out of it/never tuned it. I literally bought the bow off the classifieds, used the same arrows it came with, the only thing I did was adjust draw length. I got good groupings out to 40 yards and arrow flight "looked" good. I didn't feel confident past 40 yards. So that's where I've limited myself. I'm going to the shop next week to make sure it's tuned, I know that can shape what route I go with setup. I'm kicking myself for not doing a deeper dive and being setup before hunting. I got lucky on that cow last year and the last thing I need to be doing is going out with an untuned and not lethal enough setup.
My current arrow setup appears to be around the 405-410 total arrow weight. If I go with the proposed setup I'm thinking, I get into that 440 grain range. So I'd be trading some speed but picking up some overall kinetic energy.

 

Sounds like you made a good shot even if penetration wasn’t ideal. Your current setup definitely has some limitations, especially with the big 2.25” mechanical. At your draw length and weight, the 400 spine is borderline soft, especially with 125 up front. You’re right to want to tighten things up a bit if you’re planning to bump poundage.

 

The Easton Hunter Classics in 340 spine are a solid move. Heavier arrow, stiffer spine, more FOC with that 23 grain insert, all good stuff that’ll give you better penetration and broadhead flight. The Sevr 1.5 is a much more sensible choice too: still a mechanical, but with a smaller cut and better track record on elk. At 60–62 lbs draw, you’re building a much more effective

 

Well I didn't have the time to get things setup with new arrows but I did go get my bow tuned up, my draw poundage was actually only around 53lbs, so the 400 spined arrows were ok. we also noticed I was getting vane contact with the drop away rest. So we got that sorted. but I did switch to the sevr broadhead 1.5 in 125 grain. I had a 30 yard shot on a cow last weekend and had a pass thru and she piled up within 10 yards and she was done in less than 10 seconds.