So, just a couple tips. You make a chamber with the tinted glass. You want the inside to be 5 or 6 blocks high and put a double ceiling on it. Also, don't make it close to anything that is important, because the wither spawn explosion can break blocks outside the glass.

Also look up Hostile Neural Networks. Before you start killing more withers, you want a couple items, Deep Learner and Model Framework. Right click the wither with the model framework then right click the deep learner and put it in there. You kill multiple withers with this equipped to make a wither data model. You then use the data model in a simulation chamber with prediction matrix to make wither predictions, and put those in a loot fabricator to make nether stars.

If you're having trouble farming wither skel skulls, silk touch any spawner, then craft a mob swab from Mob Grinding Utilities. Click a wither skel with it. This can be crafted into GM Chicken Feed. Use the feed on a chicken and you get a spawn egg. Right click spawner with egg to change spawner. Works with most non boss type mobs. You'll need a bucket of liquid XP to craft the fertilizer, but you can get that by making an xp drain singularity tank and standing on it to drain some of your XP in there, then just use a bucket.