ADD MORE VG aka vegetable glycerin. it thickens the juice. Juice base (like %80 of the bottle is VG and or PG propelyne glycol).
VG will make more vapor and smoother vape but lower the flavor and nic amount but you might not need to add much. I believe the humco "glycerin' they sell at Walmart for a couple bucks is the same stuff we vape (and it's vegetable based and not beef fat or something else). There's a ton of threads about that being "the same stuff" and I bought it on vacation once and it seemed the same (or just order some vaping VG online for like $12 shipped, check ebay).
PG is thinner and more 'peppery' aka harsh if you ask me but some people like that.
If you are building you own coils which it doesn't sound like, but if so, add a thicker wick.
Heat could also be a factor if you live where it's hot. On a really hot summer day here around 100 degrees and/or kept in a car, the juice gets thin and can leak.
Tanks with juice flow would fix all your problems, just close up the flow a bit (Beyond me why they even make tanks without juice flow these days).
As for juice being expensive, learn to DIY, but check popular recipes because it can be very hit or miss if you just buy flavors and mix. But it is VERY easy to DIY juice and cheap and you can make it thicker to not leak but still have same nic level you want and still have plenty of flavor. Usually flavor is PG or alcohol based which is thin, but they do make VG based flavors but they are not as flavorful unless you use a lot (PG or alcohol 'carry' the flavor much better).
