Just notice that the speed Limewire reports is KB/sec (Kilobytes per second), while the speed report you get from online speed tests is in Kbps (Kilobits per second). As there are 8 bits in a byte, you need to divide the speed report you get by 8 to get the values in KB/sec. For example your above speed report would work out as 75KB/sec down, 17.5KB/sec up, which means that your Limewire transfer peaks out at just over your available line capacity.
I would recommend performing a speed test several times throughout the evening to check for contention. To rule out a possible false speed report caused by the link between you and the speed test site, I would also recommend testing a few online speed test sites and choosing the one that gives the fastest report. For example, in Ireland, IrishIspTest.com gives a pretty accurate result. If you live in the UK and prefer to avoid using a Java based test, BT Broadband has several test downloads ranging from 5MB to 15MB on http://www.btopenworld.co.uk/speedtest Download the 5MB one and when the transfer rate settles, this is roughly your speed in KB/s. If you have a 2Mb or faster link, you may need to try the 10MB or 15MB test files in order for the transfer rate to settle before the file finishes downloading.
In Ireland, Irish ISPs set the customer’s link to the exact speed they advertise. For example, if someone subscribes to the 2Mb link, they are connected at 2048kbps. However, with the overhead on traffic being carried over the network, the actual maximum transfer rate is something like 1744Mbps for this link (from my experience with several ISPs). ISPs in the UK tend to connect people at a slightly higher rate than what they advertise in order for the actual transfer rate to be closer to what they advertise. For example, you can easily expect to get up to 1.9Mbps on a 2Mb connection in the UK depending on the ISP. To get your Limewire speed in kbps, multiply the speed of your download by 8.
As neild, mentioned, check your connection settings in Limewire just to make sure that these are not causing an artificial bottleneck.