I suggest that you consolidate your borders and restructure your armies.

With most of your holdings are working to their max economic capacity (namely those mines and ports), i suggest you spend your mnai in 'buying' Massalia and Tolosa from the arverni (if they refuse, just purge those greenskins). The land corridor along with the military ports will help greatly in shifting forces, especially when u have highways built.

I'm assuming that your full stacks are roman troops (consular armies). 7-8 full stacks is a bit overkill to be honest, along with the logistics strain of moving your armies and their replacement troops from italy. You generally really only need no more than 4 stacks at the very most (I only used 2 in my own romaioi save, 1 camillian 1 polybian). Station them in Italy when you don't need to use them/ the very occasional retrain. These will be your campaigning taskforces.

Along your border settlements, maintain using local troops at least 2 units of solid spearmen and 2 units of ARCHERS (not slinger, the fire arrows help a lot killing siege engines) as garrison. Use more accordingly in settlements on hostile borders. Also, in key locations (bridges, main paths etc) on your borders, set up forts (again using local troops) consisting of 2 line units, 2 levy type units and 2 range units (preferably archers, but javalin works wonders too). Their purpose would be to delay and whittle down any forces that come within your borders (forts take 4 turns to besiege, buying your 1 year of time, as well as grinding down a good deal of their troops if they choose to attack). You may use more along hostile borders, or even more layers of forts (those bridges in northern africa).

Keep local half-full stacks consisting of local field troops of that region led by mercenary generals to deal with rebels and/or defending against incursions. they're generally cheaper and easier to maintain compared to shipping troops from Italy, and respond faster to threats too. When not rebel swatting, keep them near key borders, it helps make your allies a little more faithful (and your enemies less aggressive...hopefully). Remember to keep swarms of spies, assassins and diplomats near your borders at all times and assassinate all spies and diplomats that come close/within your reach. If you have business to deal with the said diplomat, kill him the moment it is done. (I find they tend to invoke machinations and conspiracies against the human player). The only problem with this method of keeping your forces would be that africa yields you no proper troops for your local 'field army', just use one of the many stack you currently have instead, then gradually replace them with the greeks from sicily. You may keep more than one in each region if it's particularly hot.

Judging from the map u provided, along with the areas I advised your to purchase off the greenskins. Your forces will consist of (not including those border forts aka lime):
-Up to 4 stacks of Roman armies. (You really only need 2, 3 if you're really paranoid)
-7 stacks of local field armies. (half or less each in southern Iberia and west africa, 2 near Lepki to hold off the yellow fever, 1 in the northern Iberia, 1 between Tolosa and Massalia, 1 near Patavium and 1 in Macedonia)

You may seem to be fielding more stacks than before, but the cost to maintain would be considerably lower, and shorter supply lines. Use them with your forts and you find then very efficient in holding off the enemy stack after stack. Also, after roughly 10 years, you'll find your main italian armies filled with silver chevrons (just remember to merge in replacements as soon as you have the chance to, i find they gain exp faster than retraining...and more realistic too). If you want to expand your borders, prepare the garrison troops for the target region, use your elite roman army to spearhead the attack, then use the closest local field army to follow through while your Roman army regroups and merge in replacements.

Other than Tolosa and Massalia, I suggest you leave (or even ceacefire) the greenskins alone for the moment. Make peace with KH, you're not even bordering with them. As for the yellow fever, I suggest you do a long distance naval raid on their core settlements (enslave the whole lot, tear everything down). Withdraw the moment large forces come after you with pointy sticks. It'll will take quite some time for the Ptolemies to rebuild after each sack. Rinse and Repeat. (if you are very evil, i suggest giving them to AS after u sacked it)