Dude, proto suits are meant for PC, not pub matches. If you could lose a couple proto suits (which is only possible as a logi) and still profit, then why would anyone play PC. Here's a tip, don't try to proto stomp if you'd don't got the wallet or skill for it.

Proto stomper have the ISK to do so, and usually the skill. Not saying it is, never did. But proto stomping is a completely different issue. And PC's do give millions of ISK, only if you win.

The new payout cap is too low. Probably why the team with most BRIGADIER wins, unlimited proto.

Payout is largely based off of how much ISK the other team loses. If the other team has a ton of losses, your payout will be larger. While placement on the leaderboards has some effect in ISK payouts, Warpoints are typically more tied to SP generation than it is to ISK payouts.

In other words, the more you kill and the more money the other team spends, the more money your team will make overall.

Vehicles in Pubs can be hit or miss, I've had games where I've lost a few million vs a group of tanks, and I've had games where I've gained over a million because of so many vehicles being destroyed. Overall even as a vehicle specialist I think the payouts aren't bad it's difficult to budget your own money according to your own skill level. I'm not saying your a scrub or your bad at the game, but you do have to realize and make a budget for yourself for every so many games.

You could do 1 thing, but you can't be too worried about your K/D ratio... Just go 1 week running nothing but free or near free suits in ambush... Doing this you should have a fair amount of ISK just don't go too crazy on the spending...

To OP: the rewards and pricing in this game reflect the initial design principles of risk vs. reward and in isolation are fairly sound.
However through various ill thought out mechanics and choices on CCPs part (eg. district locking, asset buybacks at the end of beta, alt farming etc.) the curent isk distribution has skewed this early principle well beyond the fairness it was supposed to create.

Many people can field what they want when they want and many can't - don't listen to those who tell you you can't run proto in pubs, that is your choice alone. But match payouts are unlikely to change as you requested and I don't think they should either.

So you are left with the one truism the has been constant throughout new eden - adapt or die.

Suggestions:
1. Run a cheaper fit - if you're going 20/2 it sounds like you would do ok in adv or even basic.
2. Spend some cash - pick up a combat pack for -ú4 (or whatever it costs in your currency) that gives you 400 suits adv and proto plus 400 weapons and modules galore. That should give you enough to earn 20 million over a few weeks, buy one a month for 3 months and you'll have isk enough for the next 6 months.
3. Beg
4. Borrow
5. Steal
6. Ring in PC
7. Sell assets
8. Run in a squad with decent logis to keep you alive

Whilst I have some sympathy that you can't afford to run what some can though being in the right place at the right time, it's like what others have said you are a small business and you have to live within your means - reduce your living cost or increase your means.