I don't have any advice to offer I'm afraid, though you could check your maximum kbps in the preferences, it should not exceed your actual internet speed, latest drivers may also help and seems there are some known issues with AMD GPUs.
I've been experiencing constant crashes as well, but only since the most recent update, I use the official SL viewer but right now it seems to be crashing out on a regular basis, either telling me that the Second Life viewer has encountered a problem and needs to close, or it will just CTD without any notifications what so ever,
My specs are:
MSI MS-7816 motherboard
Intel® Core i3-4170 CPU @ 3.70GHz (4 CPUs), ~3.7GHz
12gb DDR3 RAM
Windows 10 Home Edition 64 bit
NVIDIA GeForce GTX 750 Ti
and a 1.3mbps maximum connection speed
I do get around 200 latency since I am in Australia, but it's never caused me any major issues before apart from the occasional lag storm.