Michael is right, I would leave enough troops behind in the Phillipines to prevent a breakout, and move everyone else out. There is no reason to commit valuable time and resources to reduce the Phillipines by force, when starvation will do the job for you, over time.
The 65th Bde and supporting units are enough; the same terrain bonus that makes Clark or Manila a tough nut also makes breakouts very tough. And failed attacks by the USAAFFE command are disatrous, because they burn valuable supplies.
You know all this, but for everyone's benefit: There is no reason not to bypass the Phillipines. You don't need Manila in the short run. The only risk is that the Allied player might use Clark and/or Manila for "pop-up" attacks using SB2Us or something like that. While potentially irritating, it's not a game-changer, and you can mitigate that by constant bombing of the 2 airstrips, which is a must. Even here, any old bombers will do, allowing you to use Sallys for front-line work.
Singapore, on the other hand, can only be reduced by force; and it is critical to take before moving into the Bay of Bengal. Singapore can't be starved, as even if you can get in the hex and stop LI production, it starts with over 80K supplies, enough to last awhile.
Too many IJN players, IMO, expend resources on reducing Luzon by force. It's a waste of time. You need to use that force elsewhere, like Malaya.
completely agree with QBall here. Maybe the 65th Bde is a bit too few to be 100% sure he won't breakthrough. Move the 65th out (that unit can do some damage in the southeastern DEI alone) and place there a division to keep Clark besieged. Bomb it with a couple of Sally Sentais everyday and, sooner or later, Clark will fall with ease.