Going to have to disagree a lot with SevenOfCarina.
Versus 50k missiles, you would be able to fire 120 of your 160 high agility AMMs. Yes, you wouldn't be able to flush all your AMMs against a single Box launcher volley, but for dealing with repeated volleys you will definitely have capacity to deal with them. Going with an 8 to 1 MSP to launcher ratio as they advocate, you may as well just have everything in box launchers.
If the longer ranged, lower agility missiles are intended to be anti-ship missiles, I suggest sticking a larger warhead on them. You are better off with a 60% chance to get a 2-warhead missile to hit than a 90% chance to get a 1-warhead missile to hit. Also, consider if you need the anti-ship missiles to simply be able to strike the enemy before they reach beam range, in which case 5 mkm would be plenty.
On the subject of armor, that depends. A fleet built on the concept of shooting down enemy missiles is only going to worry about missiles that can exhaust your own AMMs, such as enemy AMM spam. Having beam point defense to deal with rapid fire missiles in smaller volleys is a good complement to AMMs which can blunt box launcher volleys.
I agree that the speed is a bit low, but as an escort limited to the speed of the Jump Tender, that isn't a bad concept. One advantage of large magazine designs is you can use them as colliers for a long time after they fall behind the tech curve. They have the endurance and efficiency to be useful for shuttling missiles to colonies.
One thing I disagree with is trying to directly escort survey ships. That is WAY too consumptive of fuel. Being in the same system and responding to threats, that is different. You aren't so much escorting them directly as using them as bait to draw out an enemy, so that the other survey ships can complete their tasks.
As a starting fleet, it is not bad, but you will want some faster beam ships to complement them. Something to kill the enemy efficiently once you have run them out of missiles. You can use your anti-ship missiles to pick apart the most dangerous enemy beam ships, and hopefully not have huge logistics problems of replacing thousands of missiles every fight.
Going for a single fleet speed is something a lot of people suggest, but it is a mistake. Have a strategic speed that everybody can match, that has your tender, your point defense, and any support ships. But your beam fleet should be faster, perhaps twice as fast. Because controlling the range is FAR more important for a beam ship than for a point defense ship.